stuffing box on a sailboat

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Re-Packing A Traditional Stuffing Box

The Stuffing Box (click any image to see a larger version)

While digging around in some old boat parts boxes I found a stuffing box from an older sailboat. I though it would be a good time to rig it up in my shop and illustrate how to replace the packing material inside one of these tried & true work horse style stuffing boxes. Stuffing boxes are also called stuffing glands, packing glands or packing boxes but they are really all the same thing.

For illustrative purposes I cleaned the stuffing box of it’s oxidation and grime with my a stainless wire brush. I used a piece of 1″ diameter stainless steel as my makeshift prop shaft to complete the picture and present this as it would look inside a boat.

In this photo what you are actually seeing are two nuts not just one. The larger of the two is where the flax resides. The thin nut, on the left, is the locking-nut . Once re-packed, & properly adjusted, you lock these nuts together with two large wrenches.

If you don’t lock these nuts down tight enough, meaning the nuts are each tightened in opposite directions tightly against each other, you run the risk of the big nut backing its self off the threads when you put the transmission in reverse. Over the decades there have been more than a few boats sunk by improper adjustments of the stuffing box nuts.

IMPORTANT: I am not advocating the use of perforated hose clamps on a stuffing box. I would strongly urge you to use non-perforated AWAB 316 SS hose clamps instead. This article was done in my shop and I used what was easily on hand to make the article work. On the day I shot this I did not have any  non-perforated AWAB hose clamps to fit this hose. The article is about re-packing the stuffing box not about the hose clamps.

Stuffing Box Wrenches

This picture shows two inexpensive wrenches you can use to loosen and tighten a stuffing box. One wrench is a traditional pipe wrench and the other is a spanner wrench designed for a sink drain. Both of these wrenches are available at Home Depot or any hardware store.

I find it easier to use the pipe wrench on the small & thin locking nut and the spanner wrench on the big nut. It’s very important to use wrenches that fit the nuts well. Water pump pliers will, in many cases, not work very well or will not get the nuts tight enough after adjustment. Use good wrenches and not pliers for safety’s sake.

TIP: While I show these wrenches as wrenches you can use I would urge you to purchase as set of proper stuffing box wrenches for your particular box. Buck Algonquin and others sell packing box wrenches and they can be purchased from vendors such as Hamilton Marine.

If you’ve tried the above method and the nuts don’t break apart use a little bit of PB Blaster or Kroil. Products such as WD40  DO NOT WORK WELL AS A PENETRATING OIL . I can’t stress enough how much of a difference there is between a product like PB Blaster or Kroil and lousy penetrating products such as WD40.

Here’s a direct quote from a reader who used this article for directions. Unfortunately after three hours, Liquid Wrench, and a broken tool he gave up and emailed me for advice:

Begin Quote:

“I knew where the cap and the locking nut were, I just couldn’t budge them. I went out and bought some of the PB Blaster you advised me about and sprayed it on. Ten minutes after spraying it broke loose. PBB rules. Thanks”

Tightening & Loosening

Here’s another view of the wrenches and the process.

* When loosening the nuts the two wrenches are moved towards each other

* When tightening the nuts the wrenches (as shown here) are moved away from each other.

Broken Free

In this photo it’s much easier to see the two distinct nuts. The thin one on the left is the locking nut and the big thick nut on the right is the packing nut.

This photo shows the threaded male end of bronze stuffing box and the packing-nut or the female end of the stuffing box separated from the male end. The white PVC pipe on the left is my dummy-mock-up of a vessels fiberglass shaft log.

The rubber hose connects the bronze stuffing box to the boats shaft log and needs to be replaced periodically .

If this rubber hose cracks, deteriorates or starts leaking, it can sink your boat. Most references suggest replacing the rubber stuffing box hose every seven to ten years.

Correct Hose vs. Incorrect Hose

If you happen have your shaft out, this makes for an opportune time to replace your stuffing box hose as well.

The thicker hose on top is specifically made for stuffing boxes. It’s a robust 6 ply hose , and meant to take the abuses of a drive train installation. The stuffing box hose on top is made by Buck Algonquin. Buck Algonquin a US manufacturer of quality bronze packing boxes and other drive-line components.

This Buck Algonquin hose, sized for a 1 3/4″ shaft log, can be purchased from Hamilton Marine for about $9.00 or less.

IMPORTANT: Please do not use wet exhaust hose, as  shown below the Buck Algonquin hose. There is a big difference between actual stuffing box hose and a wet exhaust or plumbing hose. Seek out hose specifically made for stuffing boxes.

If you can’t find Buck Algonquin hose in the size you need you could use a minimum of 4 ply non-wire reinforced hose. Please do not use 2 ply or 2 ply wire reinforced hose. A stuffing box is no place for wire reinforced hose.

WRONG HOSE… D’oh……

There are vast difference in hoses and most are not at all suitable for a stuffing box application. I take many pictures of bad installations but a reader sent me this one. This one takes the cake.

• Use the right hose
• Replace on a 7-10 year +/- cycle

Please do not use the wrong hose. This boat came darn close to sinking. Use 4 ply minimum, non-wire reinforced hose. The Buck Algonquin product is six-ply .

Incorrectly Clamped

Double hose clamps won’t do any good, and can actually be detrimental, if they are not clamping anything but air. Look at the inner clap on the shaft log. It is not clamping anything but rubber. Oops……

Please be sure your hose clamps are clamping what they are intended to clamp .

Stuffing Nut Shown WIth Old Flax Still In It

When you are replacing your packing you will most likely never see this view unless you remove the transmission coupling and take the nut off. When removing the flax, with a pick, this is what you are trying to dig out! I took this photo to show the female nut with the old flax still in it. You can see the shiny surface where it meets the shaft and the thickness (3/16) of the flax its self.

Today we are lucky to have more availability than the old stand-by antique plant based packing materials such as flax packing . Flax packing is prone to rot, expansion & contraction, which messe with adjustment, and has a higher propensity to score shafting.

Packing Material Types:

Flax Packing – This packing material is derived from flax plants and they require a higher drip rate for lubrication. Most flax packing materials are impregnated with paraffin/wax and animal lard. Some flax packing materials are impregnated with Teflon. Kind of like putting lip-stick on a pig. This type of packing absorbs water, swells/shrinks and is not well suited for vessels that get hauled for winter storage. It is an inexpensive packing but low in performance.

Synthetic Packing – While often called “ synthetic packing ” the individual yarns the braid is made from are most often made of acrylic. These packing materials absorb less water, are less prone to rot and are quite often impregnated with Teflon, paraffin or lard as a lube. The have a lower temperature performance rating than Teflon yarns and sit in-between flax and Teflon for performance. They require a medium drip-rate for optimal lubrication.

Teflon Packing- This packing material does not swell, does not rot and will stay adjusted longer. This type of packing is optimal for boats that are dry stored yearly and haul / launch usually requires no additional adjustments due to dry-out and re-absorb.. They also are available with added lubrication . These packing products are galvanically inert but are not readily available in the marine market.

Graphite Extruded Teflon – These products usually have the graphite lube physically extruded into the Teflon yarn before it is braided . Extruding the lubricant (graphite), mixed into the yarn, is a far superior process than “ impregnating ” the product after the extrusion & braiding process. This material offers the best heat transfer due to graphite’s inherent ability to transfer heat rapidly. The addition of graphite, as the performance lubrication, allows for minimal dripping and longer times between adjustments. The down side to graphite impregnated packing’s is that graphite is the most noble element on the galvanic scale. In other words graphite packing materials can cause localized damage to shafting and can increase anode erosion rates. The ABYC and Western Branch Metals (The largest prop shafting manufacturer in the US) specifically disallow the use of graphite packing materials. With the great performance come some cautions and risks.

This particular stuffing box is a 1 inch stuffing box and uses three rings 3/16 flax packing. These two surfaces, where the shaft and packing meet, tend to polish each other smooth, and if over tightened, can lead to premature shaft wear or excessive heat.

Over tightening of the packing-nut, and running the stuffing box with no water drips, will eventually wear a grove in the prop shaft and ruin it. It’s very important to allow a few drops of water per minute, when the shaft is spinning, for lubrication. Even the newer synthetic W.L. Gore GFO packing should have a drip or two per minute with the shaft spinning.

Empty Stuffing Box Nut

This is what the female stuffing box nut should look like, after you have removed all the old packing from it.

My Home Made Pick

I can’t remember where I found this pick, perhaps Sears, but it used to be straight and was designed for removing engine seals! I used a blow torch and a bench vice to create my own, custom made, flax removal tool and it works remarkably well. Even a sheet rock screw can be used to remove flax but in tight spaces it’s nice to have a couple of bends in your flax removal tool.

Getting Ready To Dig Out The Old Flax

In this photo I left about an inch between the male end of the stuffing box and the female nut. This is typical of the space you’ll have on many production boats.

WARNING: If you have not attempted this type of DIY job before it’s best to do it with the boat out of the water for obvious reasons. With the female flax nut removed water will flow into the boat from between the male end of the box and the shaft. Please be careful.

Grabbing The Flax

What you can’t see in this picture is the sharp end of my pick has been firmly embedded into the first flax ring and I’m ready to pull it out of the nut.

Removing Flax With a Pick

Success! The first ring of packing is on its way out..

Packing Nut Off & Old Packing Out

I don’t advise, and can’t with a good conscience, suggest the use of “miracle lubes” such as the moldable packing materials like the; “ West Marine Moldable Packing Kit “. While many have claimed good success with these miracle lubes others have not, including myself.

On a boat we had in 2000 I installed the “ West Marine Moldable Dripless Stuffing Kit ” and it eventually became a nightmare. The green stuff in the image is the “ moldable clay ” shown with the two rings of packing that came out of the female stuffing nut.

Article Edit: Since writing this article I’ve conducted extensive temperature testing of packing glands with a fixed temp probe mounted directly to a traditional bronze stuffing box. I have measured this now for over 6 years with various products. A digital temp display was mounted in the cockpit. What I have learned is that packing gland temperatures can be anything but static .

Why? What I discovered is that air can become entrapped in the shaft log and with no cooling water, meaning no drips, you can, quite suddenly and without warning, develop a massive temp spike. Some vessels are more prone to this than others. Our old Catalina 36 was quite prone to this issue. Even after converting to a PSS dripless seal, before they introduced the vent, I found that boat needed to be burped, due to entrapped air , multiple times per season.

At one point during testing we had motored for over 3 hours using a graphite impregnated packing set for less than a drip every three to four minutes. The temp stayed at steady at 85-102F for over three hours. We hit some prop wash from a large yacht and within 3-4 minutes the packing gland was pushing 300F. Ouch!  This same type of event happened about 14-16 times over a 6 month period using a very low drip rate. My goal in testing was to find the happy medium for the least-drips to the most consistently stable temps. I adjusted the gland for 1 drip per minute and the temp spikes were gone.

This is why stuffing boxes are intended to drip some. When they drip they also displace any entrapped air. Not all boats are prone to entrapped air in the shaft log, but many are. The simple act of backing down on an anchor can force air bubbles up into the shaft log and with no drip there’s no way for the air to escape.

It is my best guess that this is what happened with our “miracle clay” packing…

Packing Nut Showing Syntef & Teflon Flax

The idea behind this green moldable clay is that it will make your traditional stuffing box dripless . To install it you insert the first ring of flax, then pack in the green clay like substance and insert the second ring making, in essence, a green-stuff sandwich.

While the idea of a dripless shaft seal is not new this stuff, in my opinion, is probably not the ideal way to go dripless . Not only is it very, very tough to remove with a pick, and replace once installed, it also did not work as advertised for me. I would also note that since writing this article numerous readers have emailed me & reported similar overheating events.

What Happened?

Remember when I talked about air entrapment in a packing gland causing temp spikes, I suspect this was it. My suspicion is that the box became entrapped with air, the green-stuff then overheated by running totally dry. Running dry melted the green goo and it oozed out and completely plugged the male end of the stuffing box with a thick black sediment . This sediment now kept the stuffing box air entrapped and eventually a burning smell notified me to the problem in the bilge.

This black goo/sediment can only be described as, remnants of the green-goo lubricant . This gray/black goo totally plugged the stuffing box essentially preventing any cooling or lubricating water from getting to the female nut. If left alone for a long enough period it could have ruined the prop shaft or potentially started a fire or damaged the packing hose. When I went to inspect the burning smell I reached out to touch the stuffing box and blistered my finger tips with burns.

Again, many folks claim good success with the miracle-goo so take my advice as cautionary only and do your own research beyond what I’ve said.

Keep in mind that this box had been run in excess of 240 engine hours at the time of the melt down and this does not include the shaft rotation time for the prop free spinning while sailing . . Air entrapment is real, it can happen and does happen and if the box can’t drip, it can entrap air and  create problems. Even PSS seals are now plumbed to let air escape from the shaft log.

This Mess Of Green-Goo Really Messed Up This Stuffing Box

If you clicked on this picture to enlarge it you can see the black goo residue on the shaft caused by the green-goo moldable packing that had over heated and was clogging the stuffing box.

IMPORTANT: All traditional stuffing boxes require water for lubrication and this dripless-clay totally plugged the area between the shaft and the male end of the of the stuffing box as seen in the picture.

Even with the female nut totally removed, in the water, I was getting, at best, 4 drips per minute with the nut off! Please be cautious running any traditional stuffing box dripless.

Dripless Vs. Drip-Less

Once again the sleazy marketing mavens have muddied the waters and done their best to mislead the average boater.

Dripless = A stuffing box that has zero drips

Drip-Less = A stuffing box that drip s less but still needs to drip some

Dripless is a term that is best forgotten in regards to standard traditional stuffing boxes. The proper term is drip-less or a box that will drip less often.

The green-goo stuffing box actually got so hot, from the lack of water lubrication, that it started to smell and I burned & blistered my fingers when checking on it. This is what eventually can happen when you opt for dripless vs. drips less.

Keep in mind this did not happen instantaneously and took approx 240 hours of run time to accumulate enough Syntef/Clay gunk to clog the stuffing box. It ran at what I thought were normal temps during and after break in as I measured it with an infrared thermometer.

I now know that spot temp checks do not tell the whole story . Temp spikes and excessive heat are likely what caused this stuff to clog my shaft log over time. In my opinion this stuff is not suitable for a “tight” shaft log where you don’t have sufficient clearance between the shaft and the male end of the stuffing box.

How does air get in there? Docking or anchoring with quick blasts of reverse can send  air bubbles up into the shaft log. Sailing in rough weather can also lead to air entrapment. If the shaft log is totally sealed or “ dripless ” the air accumulates until the box has no lubrication.

There is a good reason traditional style stuffing boxes are meant to drip. These newer packing materials should not be considered “ dripless ” and should be consider to drip less often .

Beyond entrapped air causing lubrication issues, stagnant water in the shaft log can lead to crevice corrosion of a stainless alloy prop shaft, as you’ll see below.

Why It Should Drip Some

Real Tobin Bronze shafting has been long gone for many years now, and as such, alloys in the stainless family, such as Aqumet & Nitronic are now being used it its place. These alloys, like type 304 and 316 SS, can suffer from a phenomenon called crevice corrosion.

Crevice corrosion is worst when a stainless alloy is in contact with seawater, and also oxygen starved . Crevice corrosion can also happen to bolts between wet or leaking decks, chain plates, or in stainless keel bolts where they pass through the keel stub. Most folks are aware of chain plate and keel bolt corrosion but are often unaware that it can also happen to stainless alloy prop shafts. Allowing a packing box to drip helps to keep the water in the shaft log from becoming oxygen depleted .

Over the last 10-15 years there has been a startling rise in crevice corrosion of prop shafting. With the newer packing materials, and misleading advertising, that use phrases like drip-less, the problems have only continue to escalate . The unclear marketing has caused DIY’s & professionals alike to think it means “ dripless ” not drips less . In light of this muddy marketing owners have been starving the packing box area of oxygen by not allowing any fresh oxygenated water to pass through it.

Going full dripless can potentially lead to the destruction of your prop shafting from the effects of crevice corrosion. While some packing materials such as Gore GFO, Ultra-X or GTU may be able to be adjusted to be mostly dry, and still some what cool to the touch, it’s still a poor idea from a crevice corrosion stand point.

Another pit fall, when a stuffing box is run totally sealed and “ dripless “, is that they can trap air up in the shaft log. All it takes is a quick blast of reverse, and the resulting bubbles forced up and in. Sailing in rough weather can also lead to entrapped air in the shaft log. Once enough air becomes trapped up in the shaft log the packing box, you thought was cool to the touch, begins cooking while you least expect it.

If a stuffing box is allowed to drip, even at a slow rate , it allows for excellent cooling, longer shaft life, less opportunity for crevice corrosion and less opportunity for trapped air to run the box in a totally dry state and cook it.

0.05″ Of Shaft Wear

This shaft had roughly 0.05″ of stuffing box wear and was deemed scrap metal by the shafting shop. This owner was using a Teflon impregnated natural flax and thought when the advertising said “ drip-less ” that it meant it was supposed to be “ dripless “. This was an expensive mistake you should aim to not repeat.

New & Old Packing

This photo shows the old packing with the “miracle clay” and the new GTU packing. GTU is a knock off of Gore GFO, but it frays worse due to the poorer braid design.

The Gore is the one of the best of the flax type packing materials in terms of heat dissipation but it is at the very, very top of the galvanic scale, which can cause other issues.

These packing materials also need a few drips per minute to run cool and not damage the shaft. My one complaint with this GTU packing, made by Western Pacific Trading and sold through West Marine, is that it tends to fray easily and does not make the cleanest cuts even when using a brand new razor blade.

Scrap Tubing As A Cutting Jig

Many sail boats have a 1 1/4″, 1 1/8″, 1″ or 7/8″ inch prop shaft and a piece of scrap dodger tube, in your shaft size , works great as a cutting jig for new packing rings.

Use a set of calipers to make sure your “jig” of choice is the same O.D. as your prop shaft and then cut away. I usually cut the rings in this manner but you could also cut them on the actual prop shaft too.

Please cut the rings on the outside of the boat where the shaft exits the hull between the strut and the hull and not at the stuffing box. If you cut the rings on the shaft, at the stuffing box, you run the risk of scoring the shaft and causing a burr that can damage the new packing and inevitably leak more until the burr gets polished away from the friction. This could take a very long time unless you are in heavily silt laden water…

Cutting New Rings – Sub-Optimal

This may get a little confusing but there actually is a optimal way and a sub-optimal way to cut your packing rings.

In this photo I am holding my razor blade at a 45 degree angle parallel to the shaft. Unfortunately if I cut the rings in this manner they do not seal quite as well. Yes, it will work but it is not optimal . Because the shaft nut does not compress the flax on the circumference, like the action created by a hose clamp, cutting it 45 degrees & parallel creates a less than optimal seal .

Cutting New Rings – Optimal Method

In this picture it’s easier to see the 45 degree cut and how the two ends of the packing will join together. The packing nut will actually compress these two ends together and create a better butt-joint than if they were cut vertically for a circumference (think hose clamp) type compression. I told you this was a little confusing.

Once the ring is cut be very, very careful to minimize fraying before installing it. If you’re using impregnated PTFE or traditional flax packing fraying is usually not an issue. With GTU or Gore GFO etc. fraying can be an issue.

IMPORTANT: When you cut rings this way they will  not wind up the correct length. Cut it and then shave one end down until you get the correct fit over the shaft where the two ends butt perfectly. A perfect fit is with the rings neither being too large, so as to cause a gap with the ends butted, or too small so the ends won’t quite butt together..

Here’s Why

This is a good illustration of why the cut should be made the way I have shown above. The compression of the packing nut seals the butted ends together nearly perfectly. Little details like this make for an easily adjusted stuffing box with a correct drip to temp ratio.

Three Packing Rings Installed

This photo shows three rings installed. This packing nut fits three rings, some don’t and it’s not a huge deal if one does not fit more than two rings. Three rings is preferred and considered optimal. You can also go to four but beyond that cooling issues can happen.

Thread engagement is critical and my personal preference is for four full thread peaks of engagement between the female nut and male stuffing box threads. This is four thread peaks with three rings installed and seated.

Old Teflon RIngs & Syntef Shown With GTU Rings

Here are two of the new GTU rings and the old stuff. Note the fraying I discussed earlier even though I tried to minimize it. I have discovered that Western Pacific Tradings GTU frays considerably more than Gore GFO or Duramx Ultra-X. GFO and Ultra-X barely fray at all when cut. This is due to the braiding process used.

Perhaps, to prevent fraying with GTU, you could heat up a little wax in a bowl and as soon as you cut the ring dip the ends in the wax like whipping a line. There is actually a fair amount man-handling, of the rings, between the time when they are cut and inserted and some measure of fray prevention should be attempted when using Western Pacific Trading GTU or just use GFO or Ultra-X.

Different Braider

The product I used above for this article was Western Pacific Trading GTU from West Marine. Initially I thought it was some Gore GFO I had lying around but GFO has the words “ GFO ” embossed right on the packing and after going through the photos carefully I could not find the silk screened GFO logo.

I had never had Gore’s GFO fray but the GTU product does. The photo to the left is Duramax Ultra-X which has a very similar construction, and braid, to Gore’s GFO. It does not fray when cut like GTU does.

Johnson-Duramax Ultra-X can be purchased by the foot from Hamilton Maine and it cuts cleanly.

Duramax Ultra-X Cuts Cleanly

Here’s an image of a 45 degree cut. This one comes up a bit on the short side so be careful in your cutting.

This ring was cut from Duramax Ultra-X. It is important to keep in mind that these graphite impregnated/extruded packing materials can dull a razor blade quickly so rotate in a new blade if the old one is cutting poorly. Razor blades are cheap.

Start With Your Cut Rings Ready

One of the last things you want to do, if changing your packing in the water, is to cut your rings during the project. Please do yourself a favor and pre-cut your rings.

If you’re new at this I would recommend starting with 4-5 rings as you may damage one or two in the installation process.

Edit and Answers:

I’ve received far too many emails asking what this packing material is to ignore them, so here are the details.

This is the packing material I now use. It has been in the development and testing stages since 2013. Unfortunately it is not yet on the market and is still in the testing stages. As a marine electrician and corrosion specialist I have all but stopped using the graphite impregnated packing materials I used when I initially wrote this article back in the early 2000’s. They perform quite well, but as I discovered, can lead to a host of other issues most notably, galvanic incompatibility issues. I discuss this further down in this article.

This high performance non-graphite packing, SynBraid®, is a 100% galvanically inert synthetic high performance packing, not a “PTFE infused” product with acrylic or flax yarns making up the braid. The SynBraid® yarns are actually extruded with the proprietary lubricant in the yarn not “infused” after the yarns are extruded. I expect SynBraid® to be on the market sometime in early 2018.

Mark The Nut Where Your Seams Are

When doing this in a boat it is a very good idea to mark the exterior of the nut where each seam is so you can stagger them. Use a packing tool like I show below to compress them into the nut. Only when all rings are in the nut can you then tighten it.

Tightening the nut to seat the packing, especially with the newer more slippery packing braids, can move the seam and you’ll now be blind as to where your seams are and will need a dental mirror to confirm seal position.

You will be best to make yourself a packing seating tool.

New Packing Rings

This is the last step. In this picture I have two of the three rings wrapped around the shaft in a stepped and alternated order.

NOTE: Please ignore the fraying . This was not a real boat and in the process of photographing this I man handled the rings far more than you would. The butt ends of the rings should not look like this.

You’ll want to offset the rings butt-joints 1/3, 1/3, 1/3 for a three ring box or 1/2 & 1/2 or said another way 12 o’clock and 6 o’clock for a two-ring box.

It’s also perfectly fine to wrap one ring at a time and push the nut over it, but without turning it, until you get all three rings into the nut and staggered. It’s best when using this method of stuffing the rings to mark the outside of the nut with a Sharpie marker where the joints are and then when all rings are in the nut, and staggered, you can finally thread the female nut onto the male part of the box.

I custom made my own tool for this & it has a similar thickness to the flax for stuffing the nut (see the tool below). I don’t advise the use of a pick to stuff the flax into the nut as this can cause significant unlaying or twisting of the flax especially with GTU. When ever possible try to get at least three rings of packing in your stuffing box as most are designed for at least three. Some nuts can actually fit four & if so go for it but make sure you still have enough exposed threads to get sufficient thread engagement for the female nut.

IMPORTANT: You really need to use the correct size packing or else you will either have overheating or leaking issues.. Going one size to0 big can eventually wear a groove in the shaft and one size too small will never seal properly. Please use due diligence to determine the proper packing size for your particular stuffing box.

The Home Made Packing Insertion Tool

Many folks have asked me how I insert the packing rings into the female nut. Well, like anything dealing with boating, it’s not always easy but can be done with a little Yankee ingenuity.

I decided that in order to keep my ring joints staggered, and to get them properly seated, I needed a new tool. I wanted a tool that was to be perfectly parallel with the prop shaft when inserting and seating the flax but that did not involve twisting the nut or threading it onto the male end . .

You need to seat the packing without causing any twisting and there were no commercially available tools to do this, so I made one. Using a screw driver will not give you the correct angle to seat the flax properly and could potentially mess up the joints or put twists in the flax rings. Seating the packing with no twists is important.

Insertion Tool Clipped On Shaft

Making this tool took less than five minutes but can really save time and headaches. To build this device I decided to use a short piece of 1-1/4 inch PVC pipe with about 1/3 of it cut out so it would fit over a 1″ shaft.

I left just enough material so it could clip itself onto the shaft and stay in place without any hand holding.

For this process I cut the 1-1/4 inch PVC pipe to 2-1/2 inches long. I then inserted this 2-1/2 inch piece into my bench vise and used a hack saw to make two more cuts. These cuts removed just enough of the 1-1/4 inch PVC to create the device.

You’re probably wondering why I used 1 1/4 inch PVC if I had a 1 inch prop shaft? Well.. I used it because it’s all I had on hand and I also own a heat gun so it was very easy to heat the PVC and wrap it around a piece of scrap 1 inch dodger tubing for a perfect heat formed fit. If you don’t own a heat gun dropping PVC into boiling water will soften it enough to mold it to the shaft.  Once it cools down it will simply click into place .

Seating The Flax

This photo shows the female nut sliding over the packing insertion tool and seating the packing rings . The tool works very well and unfortunately no one actually makes one. Hey, I bet West Marine could sell one for $85.00… ( grin )

GFO, GTU & Ultra-X Warning

WARNING : While I do like the performance of graphite impregnated packing materials such as Duramax Ultra-X, Gore GFO or Western Pacific Tradings GTU they can be potentially dangerous to underwater metals. I have used it on my own vessel but inspect the Aqualoy 22 prop shaft yearly .

“RC, Why the warning then.?”

It’s all about corrosion. Graphite is the most noble element on the galvanic scale.. As such anything in the drive train becomes anodic or sacrifices itself to the packing. Older bronze shafts, really more of a brass because they had high zinc content, can be damaged by these new high tech graphite impregnated packing materials.

The damage shown in this photo happened in one season and with intact prop shaft anodes . The shaft was in perfectly fine condition when packed, and a year later this is what it looked like.

The packing used on this shaft was Gore GFO a graphite impregnated packing. If you have a bronze shaft please use extreme caution with graphite impregnated packing materials.

I don’t tend to see these issues with Aqualoy 22 shafting but I have seen it with bronze and lower grades of stainless. Please use these packing materials carefully. If you choose them please do check on the shaft periodically.

Also, please be aware that after you install a graphite impregnated packing you will see some accelerated anode erosion rates. No dire need to be alarmed at this  but do keep up with them and check them more often until you are familiar with the new erosion rate..

Here is where the ABYC Standards come down on graphite packing :

ABYC P-6: “6.7.4 Graphite impregnated packing material shall not be used because of the possibility of galvanic incompatibility with the shaft material.”

I suspect what we are seeing in this photo is exactly the “ galvanic incompatibility ” the ABYC warns against.

We now know where the ABYC stands on graphite packing but what about the largest prop shaft manufacturer in the United States, and possibly the world, Western Branch Metals?

Western Branch Metals: “ Do not use graphite packing in the stuffing box . Instead, use a packing material that causes the least abrasion after the lubricant wears away. The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material.”

Now we have not only the ABYC but one of the largest prop shafting manufacturers on the planet both saying exactly the same thing. Do not use graphite packing’s. As they say your boat, your choice.

With all that said there are still many happy boaters who have had decent results with these graphite packing’s. Please remember however that they should not be treated as a set it and forget it packing. If using these graphite impregnated packing materials I would strongly suggest checking the shaft at least yearly .

Here’s the finished product after installing three new rings of packing material.

When initially installing the rings of packing lightly tighten the nut just until you start to feel some resistance then stop. DO NOT OVER TIGHTEN THE NUT . The final adjustment will be made after running the motor and shaft for a while.

Setting The Drip Rate

Proper adjustment for GFO, GTU or Ultra-X is up to a few drops per minute when the shaft is spinning. You’ll ideally want it adjusted for nothing more than slightly different from the sea or lake water temp, about a 15 – 20 degree differential, or slightly warmer to the touch. Measure these temps after the shaft has spun for a while.

Adjustments should be made in either half a nut-flat or “one nut-flat” (of the nut) at a time. Adjust in small increments only and not more than one full flat of the nut at a time.

W.L. Gore recommends not adjusting the stuffing box until you have run the boat in gear for about two hours of time. This allows the packing to take a set and break in some.

When adjusting other types of flax the stuffing box should be relatively cool/warmish to luke warm, at most. With traditional flax packing it should drip and must drip while the shaft is spinning.

The cooler your stuffing box runs, the longer shaft life you’ll have. With GFO they claim temps up to the 125-130F range are technically safe for the packing. In my opinion & experience monitoring stuffing box temps over a 6+ year period, 125F – 130F generally means there is not enough cooling flow through the box.

Any entrapped air, with normal temps this high, can cause a big spike in box temp. Aim for 15-20 degrees warmer than the ocean or lake temp but a little higher, with GFO, GTU or Ultra-X, should not kill the deal .

Some boxes will even drip when the shaft is not spinning and this can be entirely normal depending on the condition of your shaft. Do not get stressed if you can not make it drip free at rest as not all shafts are in good enough condition for this to always be the case. Ideally they should be but many are not.

Please do not get in the habit of tightening the stuffing box when leaving the boat . Natural flax based packing’s are not elastic and do have a memory, in a sense, and they will not necessarily return to their uncompressed state . Doing this will severely shorten the life of your packing and it will start leaking, continuously, in short order.

I generally don’t like rules-of-thumb for drip rates and really hesitated to even put one on here. My reason for this is that every shaft has differing levels of wear and thus the drip rates are usually slightly different in every installation.

The best rule of thumb I’ve found over the years is this:

Aim for the least amount of drips when the shaft is spinning but before the box develops any heat rise beyond 15-20F, beyond sea or lake temps.

Again, it’s a drip to heat ratio not necessarily just a drip ratio. Little to no heat is the most desirable. Traditional flax packing can drip as little as about 5-10 drops a minute, if adjusted correctly, while running, and this drip rate allows lubrication of the shaft.

Do not make any adjustments to the packing nut, with traditional flax, for at least 24 to 48 hours after launching as the plant based flax packing will absorb moisture and swell. This swelling can cause overheating of the stuffing box, if it’s adjusted too quickly after launch.

Premature tightening of traditional flax packing can result in potential problems. A good and safe practice is to adjust the packing by half-a-flat turns after two hours of use or until you have your drip to heat ratio correct. You can actually use an infrared thermometer, often called a pyrometer, to make this adjustment process easier but usually your hand will suffice as a good gauge.

If you want a totally dry bilge then a dripless type seal such as a PSS or Las-Drop is the way to go. I’ve provided full installation instructions for that type of seal too in another article.

Good luck & happy boating!

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One comment.

I was used to using flax packing and adding a ring every year or few. An old diesel mechanic told me that he never removes the old packing, just adds a new ring. So when I switched to Gore-GFO, I didn’t realize that it would not wear away like the flax did. So every few years I added another ring until no more would fit. Deciding to remove all the old, I was surprised to find all of the rings, maybe 6 in all, intact with no disintegration. However, I found my bronze shaft had suffered some wear, probably due to over tightening. Word to the wise: When using these newer packings, tighten only enough to just stop the drip when not running, yet allowing a slow drip when shaft is turning.

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Servicing Your Stuffing Box

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Stuffing Box

If your boat has inboard power, odds are it is fitted with a stuffing box to provide a watertight seal for the propeller shaft. Stuffing boxes are also used to seal rudder stocks that penetrate the hull below the waterline.

In principle a stuffing box is identical to the packing nut on a common faucet. Its primary components are a threaded sleeve and a hollow nut through which the shaft passes. The sleeve — or sometimes the nut — is filled with rings of braided square flax rope that has been heavily impregnated with wax and lubricants. Tightening the nut compresses this packing against the shaft, forming a watertight seal while still allowing the shaft to turn.

Water is required to lubricate conventional packing, so a properly adjusted stuffing box can be watertight when the shaft is stopped, but it must drip when the shaft is turning. Two or three drops per minute are adequate. It is not uncommon to see stuffing boxes leak at a much higher rate. This doesn't harm the shaft or the stuffing box, but the spinning shaft will sling this excess flow all over the engine compartment, leading to rampant corrosion of the shaft coupling, the transmission housing, and everything else getting sprayed. Even more disastrous, it puts an unattended boat at risk of sinking. If your stuffing box leaks more than 8 or 10 drops a minute, it needs servicing. Tightening the stuffing box nut a half turn is all that is required to reduce the leak, but the location of the stuffing box can render this job far more difficult than it should be. Access can be especially challenging in boats with V-drives and in sailboats.

The first step in stuffing box adjustment, then, is to figure out how to get two wrenches on the box--one for the lock nut and one for the adjusting nut — and how to position yourself so that you can pull on one while pushing on the other, and vice versa. You can use pipe wrenches to turn the nuts, but adjustable packing nut wrenches tend to be easier to handle in confined spaces. If the stuffing box is above a deep bilge, tie a retaining line to the wrenches before you start. With your wrenches on both nuts, hold the adjusting nut and turn the locknut clockwise to release it. Back this nut off a couple of turns. Now turn the adjusting nut clockwise until the dripping just stops.

CAUTION: Some stuffing boxes are rigidly attached to the hull, but most are connected to the shaft tube with a length of flexible hose. You do not want to twist this hose or twist the stuffing box inside the hose. If the adjusting nut does not turn easily, use a pipe wrench on the stuffing box flange — located just forward of the hose — to keep the box from turning with the nut. If the box is corroded, back off the adjusting nut several turns and wire brush the box threads bright before making the adjustment. Give threads and nuts a heavy coat of Boeshield T-9 (or some other corrosion blocker) to avoid this problem in the future.

After you make this initial adjustment, you are going to need to check the drip rate with the shaft turning. You can do this either with the boat underway or with the transmission engaged in forward and the boat securely tied in the slip. With the help of a flashlight — and a mirror if you need one — count the drops per minute. If it is more than two, tighten the adjusting nut slightly. If you cannot make this adjustment without putting body parts or clothing in dangerous proximity to the spinning shaft, stop the engine, make the adjustment, then restart it to check the drips. When the drip rate is one or two drops per minute, stop the engine. Hold the adjusting nut securely so that you do not alter the setting, then tighten the locknut against it. Before you extract yourself from your access position, carefully check the strap clamps that attach the hose to the stuffing box and to the stern tube. These inevitably corrode at the bottom, so you may need a mirror to check them. Better yet, release each one and rotate it to view all sides before retightening. Do this one clamp at a time.

After the packing nut has been tightened a few times, the packing gets so compressed that it becomes hard enough to actually wear a groove in the shaft — a condition you want to avoid. In a powerboat used regularly, the shaft packing should be replaced at least every other year. Sailboats may not need to have the packing replaced for five years or more, but when the stuffing box starts requiring frequent adjustment or if it begins to feel warm, it's time.

Repacking is straightforward. Hold the packing nut while you release the lock nut, then unscrew the adjusting nut completely to open the box. You must dig out ALL of the old packing. The easiest way to do this is with a corkscrew-like pick designed specifically for this task, but a sharpened piece of stiff wire bent 90 degrees at the end will also do the job. Take care not to scratch the shaft with either tool.

If the old packing comes out relatively intact, use it to determine what size packing you need. If it comes out as shapeless wads of fluff, then measure the space between the shaft and the inside of the packing nut to determine the correct flax size. Multiply the diameter of your shaft by 14 to get the approximate number of inches you need for 4 layers of new packing — usually sufficient.

A common mistake is winding the new packing around the shaft as a continuous piece. Packing installed this way will not seal properly. It must instead be installed as a series of stacked rings. This requires cutting the packing into lengths that just encircle the shaft with ends touching. The easy way to do this is to wrap the packing around the shaft in some accessible location and cut across the overlap with a razor knife. Curl one of your cut lengths into a ring around the shaft and push it into the stuffing box. Tamp it evenly with a small dowel or a blunt screwdriver to push it all the way to the bottom of the box. Push a second ring into the stuffing box on top of the first one, staggering the joint about 120 degrees. Add a third layer, then a fourth, each time staggering the joint. If you don't seem to have room for the fourth layer, hand tighten the adjusting nut to force the other rings deeper, then remove it again to see if this made room for an additional ring of flax. When the box is full — but not so full that the adjusting nut doesn't thread on easily — adjust it to drip two or three times per minute, as previously outlined. You will need to check this setting after the first couple of hours of use; some tightening is usually required.

Because you remove the old packing before installing new, and it is the packing that is keeping the ocean out of your boat, it should be out of the water when you do this job. If you must do it with the boat afloat, have the new packing ready to install as soon as the old is out, and drape a towel over the stuffing box to deflect the incoming flood into the bilge, where your bilge pump should handle it without difficulty. You can make the task less frantic by sealing the shaft from the outside with plumbers putty, but you will have to go into the water twice to do this, once to put the putty around the shaft, and a second time to remove it. Do not turn the shaft while the putty is in place or you will break its seal, and make sure you clean out ALL the putty when you are finished since both the stern bearing and the shaft seal depend on water flow for lubrication.

Drip-Less Packing

An alternative to conventional braided packing is Drip-Less moldable packing. The advantage of this type of packing is that it is self lubricating, which eliminates the necessity of letting the stuffing box drip. Drip-Less packing requires two retainer rings of conventional packing. You install a ring of conventional packing, then push Dripless Packing into the box until it is about three-quarters full. A second ring of conventional packing completes the job. Tighten the nut just enough to stop the box from dripping. This type of packing runs hotter than water-lubricated flax, and over tightening will generate excessive heat. The stuffing box should not be too hot to touch. Low-friction packing is six to ten times more expensive than flax, but because it rarely needs adjustment, it can be a good choice for a stuffing box that is particularly difficult to service.

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Stuffing box inspection and replacement

The stuffing box is a critical part of the boat. It allows a driveshaft to spin through the hull without allowing water to pour into the vessel. These units are often deep down in the boat, behind the engine and with limited access. On many sailboats it is often under the cockpit with side access through a locker — a dark and damp place often forgotten about until the bilge pump kicks on every few minutes and one wonders where the water might be coming from.

After removing all that resides in that locker, crawling inside and removing the small access panel — perhaps head first — the stuffing box becomes visible. Maybe it has been a few years since your last visit, but did you remember to bring two large stuffing box wrenches and a flashlight? To adjust the traditional stuffing box, you need two wrenches in order to loosen the backing nut off the cap nut. This requires two hands in this small space as well as being able to see what you are doing while breaking the nuts free. These nuts are tight and some two-handed muscle is required to free the nuts from their grip on each other. Proper wrenches are key; the adjustable stuffing box wrench might work for you, but a proper toolbox should include a set of fitted stuffing box wrenches to avoid a lot of pain and frustration.

If you succeed here, the job of adjusting the stuffing box is fairly straightforward: Tighten up the cap nut until the water stops gushing in, then retighten the two nuts together. More often than not, these nuts are corroded and, without proper tools and leverage, a tough nut to crack.

Now it’s time to crawl out of the locker, start the engine, put her in gear and re-enter that locker (don’t forget your flashlight) to see how the adjustment holds up in motion.

The stuffing box should drip ever so slightly now, say a drop every five to 10 seconds. No drip is no good because without a little bit of water lubrication, the shaft will heat up and wear over time, creating a groove in the shaft that no amount of packing can stop anymore. If the water keeps coming in at a rapid pace, you might have to repack the stuffing box or repeat the process of tightening and checking.

Don’t adjust the stuffing box while running the engine in gear! Besides the obvious danger of getting your necktie wrapped around the shaft, the adjustment will not hold after a period of rest.

On larger sailboats and trawlers, the access to the stuffing box or boxes might not be a problem and adjustments can be made while sitting down and with good light. In these cases, the traditional stuffing box is a simple, well-proven maintenance item. However, if the stuffing box is as hard to reach as described above, a dripless stuffing box might be the solution.

The dripless stuffing box does what its name suggests, leaving you with a dry bilge and, more importantly, with a low-maintenance stuffing box. No big nuts to adjust in tight spaces with big tools, no packing to replace with tweezers in this dark corner of the boat while hanging upside down in a rough sea.

The expense of refitting a dripless stuffing box is well worth it if it is installed by the boatyard, but with the proper tools, this job can be done by the handy boatowner as well.

Start by removing the prop outside the boat and the set screws in the shaft coupler inside the boat. The goal is to pull the shaft out of the coupler far enough to remove the old stuffing box off the shaft log. A shaft puller is the ideal specialty tool for this job — the dead weight of the slider jars the shaft out of the coupler in a few minutes. With the shaft pulled out of the coupler, the old stuffing box can now be removed and the shaft and shaft log can be examined.

To order a new stuffing box, the shaft size and shaft log’s outer diameter need to be measured. For example, in this case it is a 1-inch shaft and a 1.75-inch shaft log. Clean and wet sand the shaft on the surface that will receive the new stuffing box and examine it for burrs and grooves. If the shaft shows severe grooves from an overheated stuffing box as described above, there is a chance that the new stuffing box will leak (more on that later), or maybe a new shaft is needed after all. The new stuffing box by PSS comes with three key components: a nitrate bellows, a stuffing box with carbon graphite flange and a stainless steel rotor. The rotor will be attached to the shaft and turn on the graphite flange to create a watertight seal by compressing the bellows with the rotor. The polishing of this stainless steel rotor on the graphite flange with the water nearby makes for a virtually maintenance-free seal.

Install the bellows onto the shaft log and tighten the hoseclamps. The 3/8-inch nipple will point up. Connect a piece of 3/8-inch marine-grade fuel line to it, double-clamped, and run it 2 feet above the waterline. Secure this hose along the way — if it were to fall into the bilge, this vent hose would become a fill hose.

Take the rotor and pre-position a set screw in each of the two holes with a drop of thread lock. Position the shaft so the stainless steel rotor can be installed onto the shaft. This is the tricky part because the rotor has two rubber O-rings inside it that must not get damaged during this installation. That’s why wet sanding the shaft is so important. Use soapy water — not grease or penetrating oils — to slide the rotor onto the shaft. Lock the shaft into position, as it will want to walk out while you are trying to push the rotor on. Use lots of soapy water and move the rotor at least an inch past the keyway of the shaft. Prepare the key and keyway, and reinstall the shaft into the coupler. Careful tapping will position the shaft and line the key up properly.

 The shaft puller can now be used in reverse to re-install the shaft into the coupler to its old marks. The set screws can be wrenched down and seizing wire should be added. The prop can also be reinstalled. Now, the final touch on the stuffing box: The stainless steel rotor needs to be slid down the shaft to press upon the carbon graphite flange. The rotor will compress the bellows, but how much will depend on the size of the shaft. In this case, three-quarters of an inch of compression is needed for a 1-inch shaft. Mark the shaft at the point of touching just the flange, slide the rotor another three-quarters of an inch onto the shaft and tighten the set screws down. Here is the part were those old grooves on the shaft can be a problem. Test that last three-quarters of an inch and see if the groove is interfering with the rotor. Moving the bellows up or down the shaft log can relocate the final position of the rotor on the shaft. If all looks good, add the second set of set screws with thread lock glue on them as well.

When the boat is launched and commissioned, inspect and run the engine in gear and observe. The rotor and the graphite will make a perfect seal almost immediately, but a little spray might occur occasionally. It should stop after a minute — if not, a bit more compression might be needed. A poor engine alignment can cause the shaft to shake a lot and make the dripless stuffing box drip.

The stuffing box is now a lower-maintenance item and can be quickly inspected and cleaned with one hand, even if upside down in that locker.

By Ocean Navigator

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Stuffing Box Care

Only boats with inboard engines have stuffing boxes. To locate yours, trace the propeller shaft from the transmission to the point where it exits the hull. Thats where your stuffing box will be (unless you have a newer, dripless style shaft seal installed instead).

The purpose of a stuffing box is to allow the propeller shaft to exit the hull while keeping water out. The shaft is sealed by compressing packing material against it, most often by using a hollow nut that screws onto a matching fitting attached to the inboard side of the shaft log hose. Another common style features a tightening arrangement that uses a plate secured by nuts and studs on either side of the shaft.

The more you tighten either type of gland, the more the packing gets compressed against the shaft. Most packing consists of a square plaited material and comes either as traditional greased (or waxed) flax, or a more modern version impregnated with Teflon.

Corrosion and leaks are common problems youll encounter when inspecting your stuffing box. The shaft log hose (which connects the stuffing box to the hull in most installations) should also be inspected for deterioration due to age (a common problem), corroded hose clamps, etc.

Water helps lubricate the packing material so its OK for a stuffing box to leak a few drips (3 to 4 per minute) while the vessel is underway. More than that amount (say 10 drops per minute) or drips while the shaft is not turning indicates the need for adjustment and/or maintenance. A leaking stuffing box can cause a number of issues, from corrosion (the spinning shaft slings excess water all over your engine compartment) to sinkings, particularly if the boat is left unattended in the water for longer periods of time.

Packing material will harden over time (as the lubricant dries out) and gets worn away by shaft rotation, allowing water to pass and enter the vessel. When this happens, most people simply tighten the packing nut(s) to compress the packing material and stop or reduce the leak.

This works to a point, but as the packing gets smaller it also gets harder. Keep compressing it and it will eventually score the propeller shaft, which will then have to be replaced before the stuffing box will seal properly. Avoid such problems by simply replacing the packing on a regular basis.

Dripless shaft seals

Dripless Shaft Seals are an alternative to packing glands. They prevent water from entering the hull via pressure loading, typically by using a compressed rubber bellows to hold a graphite collar against a stainless steel collar. High speed vessel installations will usually have a water injection hose plumbed to the engines raw water cooling systems, which helps reduce heat generated between the two contact surfaces.

While they don’t require re-packing like traditional stuffing boxes, dripless shaft seals still have regularly scheduled maintenance requirements that must be carried out to ensure proper operation. These include periodic removal and inspection, as well as keeping the cooling hose mentioned above clear and open.

Capt. Frank Lanier is an accredited marine surveyor with over 30 years of experience in the marine industry. His website is www.captfklanier.com .

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Stuffing box help

• Thread starter Paleolithic
• Start date Mar 15, 2020
• Tags box help oday oday 28 pipe wrench stuffing stuffing box
• Oday Owner Forums
• Bigger Boats

Paleolithic

• Loosening with 14" heavy duty pipe wrench and lock nut wrench
• Spraying with WD40 Penetrating Spray (not regular WD40)
• Putting pipe wrench on and tapping with Ball Peen Hammer.
• I understand to loosen I need to grab both with wrenches and bring the wrenches together, but I'm not sure which I'm to bring up and which I'm to bring down.
• Clockwise and counterclockwise are ambiguous since I'm not sure which way is "in" if you understand me.
• If you could put it in terms of "towards port" or "towards starboard" that would be helpful.
• All I've accomplished is rotating the whole shaft with the wrenches and simultaneously cutting up my hand.
• I have Liquid Wrench coming in the mail and am hoping that works better than the WD40 Penetrating Spray.
• Make/Model/Year: 1985 O'Day 28'
• Engine: Original Universal Diesel M50 10hp

Attachments

Warren Milberg

First, i would try heat on the stuffing box with a torch, if you can do that safely. Second, rap the lock nut toward port very hard with a ball peen hammer. Really whack it. Third, put one wrench on the packing nut, the other on the lock nut and try to pull the lock nut to port. Good luck.  

Stu Jackson

Look at the threads below the lock nut. That will tell you which way to turn it.  

Davidasailor26

To loosen the locking nut we used to have a bronze bar and a hammer. Rest the bar in one of the notches on the nut and hit the other end with the hammer. I don’t remember which way it turned though. It might also be easier to access from the quarter berth. We serviced ours from there.  

twodzusfittings

If your quarter berth is on the starboard side: from the quarter berth access, turn your locking nut to the right, (away from your body). Be careful with heating it, as you will be in close quarters to the inside of the hull. Use plenty of penetrating oil and let it take its sweet time.  

I'd clean it all up first with a wire brush then spray and then heat if in water shaft will cool with sae water if out I'd use ice and torch  

Claude L.-Auger

Banging might cause severe damage to the transmission. Cleaning, Soaking with PB Blaster (or similar product), possibly heat will help. If you have room, leverage is your best friend. Clamp a pipe wrench on the packing nut with the handle resting on the floorboard in whichever sense is needed (Stu gave you the way to find out), then another on the locking nut with the handle where you can get 2 hands or possibly a cheater bar on it. Once the locking nut is loose and screwed back towards the rubber hose, the packing nut should nut be a problem to break loose. Good luck.  

Thanks all for the help, I'll be back down there this weekend to attempt again and will report back!  

Dave Groshong

Re-packing a traditional stuffing box.

Richard19068

Paleolithic said: I'm attempting from the port lazarette if that's helpful. Things I've tried: Loosening with 14" heavy duty pipe wrench and lock nut wrench Spraying with WD40 Penetrating Spray (not regular WD40) Putting pipe wrench on and tapping with Ball Peen Hammer. Questions: Which direction do I go with the lock nut and the stuffing box nut? I understand to loosen I need to grab both with wrenches and bring the wrenches together, but I'm not sure which I'm to bring up and which I'm to bring down. Clockwise and counterclockwise are ambiguous since I'm not sure which way is "in" if you understand me. If you could put it in terms of "towards port" or "towards starboard" that would be helpful. I have Liquid Wrench coming in the mail and am hoping that works better than the WD40 Penetrating Spray. Click to expand

Paleolithic said: Thanks all for the help, I'll be back down there this weekend to attempt again and will report back! Click to expand

Success! I went to Harbor Freight and got a slightly larger pipe wrench (18"). After liberal spraying with Liquid Wrench and waiting a bit, I put the smaller 14" pipe wrench on the packing nut, and leaned it against a piece of wood on the bottom hull. I put the 18" pipe wrench on the locking nut and pulled toward me and it came undone! Next was getting the actual packing out, which I had to go to the store and get picks for, but that eventually came out and I successfully put in new packing! Thanks for the recommendations all, it was a ton of help getting confirmation on which way to pull, and the different options I had available!  

Congratulations! I for one can say, each and every task that should be simple, yet ends up baffling me, is a mile stone reached when even the simplest is overcome! My posts prove it each and every time. It makes me feel good about my capabilities.  

Before you reassemble it, clean the threads so they are like new, then put some waterproof grease on them or something like never seize that you can get at auto stores. Should help next time you need to remove it. Since the stuffing box is designed to leak a small amount when running all kinds of salt and junk get on the stuffing box, when the water dries the salt is what remains.  

With modern materials - and at the low RPMs of sailboat engines, I question the need for a stuffing box to drip. The drips themselves cannot transfer appreciable thermal energy. The water only lowers the coefficient of friction to a reasonable level that protects the packing and shaft. If you use an impregnated material (PTFE, graphite, etc. see Gore) the coefficient of friction between packing and shaft is low enough without a water film. The only issue might be after launch on some hulls where an air pocket might occur. A burp procedure might be necessary in that case.  

When I installed mine, my best friend (and when it comes to boating, my mentor) asked me why I did not get the style with PTFE etc. I had talked to a very knowledgeable person at a local boat supply store, who explained for my older boat and as I was going to use the existing stuffing box, the standard packing should be used, not the more modern stuff. It makes perfect sense to me that once the stuffing rope is wet and swollen, it helps the stop of water and has minimum yet some lubrication properties. Just like jute stuffing on wooden boats. When I rebuilt my 1960 Triumph TR3 engine, one part of the rebuild was to cut similar felt packing and soak in mineral oil, before packing into the rear oil sealing cap. Very similar reasoning to this packing gland. And as a disclaimer, this is just my two cents worth, not necessarily true or proven as such.  

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Keeping Your Bilge Dry with Dripless Stuffing Boxes

Text and photos by Steve D’Antonio

Copyright © 2017

From the Masthead

There are very few quotes that truly epitomize the attraction I have for boats, and the sea.  Among my favorite is journalist E.B. White’s little-known, “If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most. A small sailing craft is not only beautiful, it is seductive and full of strange promise and the hint of trouble.”  I’d argue, of course, that it could be any craft, power or sail, large or small, her destination and from whence she hails, or the waters she plies matter not.  White’s words embody what so many of us feel when we are afloat, and in a kingdom of our own.  The “…hint of trouble” part is especially attractive to me, in that my goal is to help others avoid it, by making certain their vessels are seaworthy, reliable and safe.

I first encountered these lines over 30 years ago, while sailing aboard a 120-foot schooner, somewhere between Bermuda and the Windward Islands.  R/V Westward departed from Woods Hole, on Cape Cod in October and the sea was unsettled almost from the moment we left the harbor mouth.  I’m certain I was seasick until we turned due south nearly a week out; that’s how I know I read these lines after leaving  Bermuda on our starboard beam.  Prior to that I had no interest in anything beyond standing my watch and trying to figure out the best way to keep food down.  The ship’s library included a compilation of short sea stories, one of which was White’s, entitled, “The Sea and the Wind that Blows”, first printed in 1963, along with the above quote.   It’s short, lovely and I recommend it highly.

I share these thoughts to remind readers that while I’m a gearhead, and I revel in all things technical, my love of boats extends beyond the engine room, bilges, plumbing, batteries, wiring and systems.  In spite of my propensity towards seasickness, I enjoy being at sea; (I’m editing this column while seated in the pilothouse of a large cruising vessel) and there are few things I love more than a  lone night watch.  Above all else, I delight at the very thought of making landfall in strange and remote places, places that can only be accessed by a small craft.

This month’s Marine Systems Excellence eMagazine covers the subject of dripless stuffing boxes, I hope you find it both useful and interesting.

A new tab has been added to the SDMC website, one which includes articles written by Steve for a variety of publications including Cruising World, Ocean Navigator, PassageMaker, Professional BoatBuilder, Prop Talk, Waterway Guide and others.  Its categories include Boat Buying and Ownership Wisdom, Technical, Cruising, and Profiles and Reviews.  New articles are being added on a weekly basis; you can access it here .

Dripless Stuffing Boxes; Avoid the Pitfalls, and Keep Your Bilge Dry

Face seals rely on the spring tension created by a bellows-type hose.  The system is simple and effective.

In its traditional form the conventional stuffing box, discussed last month, carries out a vital role, allowing a spinning propeller shaft to pass from the inside to the outside of the hull, while keeping the water out.  It has worked well and reliably aboard thousands of recreational, commercial and military vessels for over a century.  It’s simple, rugged and for the most part exceptionally reliable, although it requires routine maintenance, adjustment and periodic repacking.  Varying designs and installations carry with them varying degrees of watertight integrity.

So what’s not to like?  The conventional stuffing box’s one primary failing annoys many users to no end, so much so that several manufacturers have attempted to improve on the design.   Its flaw, albeit necessary and one some perceive as fatal, is its propensity, or necessity, to leak or drip.  That drip, while irksome, serves a vital purpose, it ensures that the packing material within remains wet, lubricated and thus cool and long-lasting.  Without this vital flow of cooling water, the packing will quickly overheat, which in turn leads to more profuse leakage and after some time the potential for accelerated shaft wear.

Dripless shaft seals should be dripless, they should not leak.  In some cases they may leak slightly and initially until broken in, however, this should not last more than a few hours.  If it does, something is wrong.

A range of alternative dripless stuffing boxes are available.  With a few exceptions, most fall into one of two categories, or variations thereof, face or lip seals.  Let me be clear for those who are trying to decide whether to go dripless or not, a dry bilge enables a vessel operator to quickly identify trouble, as any water is too much water.  Dripless stuffing boxes can help users achieve this goal, at a price.  Read on.

Face seals rely on an interface between a stationary component, most often carbon graphite, and a smooth, polished rotating stainless steel ring, the rotor, which is clamped to the shaft.  The rotor is equipped with internal O rings, which establish a watertight seal between the rotor and shaft.  In order for this to work, the shaft in the area where the rotor will reside must be relatively free of nicks, scratches, pitting or other defects.  Used shafts should be cleaned following the manufacturer’s instructions, between the end of the shaft and the area where the rotor will reside.  Caution must be used when sliding the O ring-equipped rotor over the shaft’s sharp keyway, tape is often placed over this to eliminate the possibility of damage.  Because the O rings are stationary, they are somewhat tolerant of minor irregularities in he shaft surface.

A cut-away view of a lip seal.  The self-centering “bearing” can be seen at the center, and the spring retainer for the lip seal to the right.

Slight pressure is applied between the rotor and stator using spring tension, this is typically built into the bellows-type stuffing box hose, which supports the stator.  During installation the stainless ring is carefully positioned on the shaft so as to compress the spring/bellows by a pre-determined amount, thereby establishing the correct level of pressure between rotating and stationary components, and then retained in place using double-stacked cupped set screws (many of the installations I inspect lack the double set screws because installers assume the second set to be spares). Carbon graphite is tough, durable and abrasion resistant, and with just a slight film of water between it and the stainless steel ring, the system works quite well; in fact the design is ingenious in its simplicity.

Face seals rely on stacked set screws to secure the rotor.  In many cases the second set screw is, like the one shown here, not installed.

Ensuring that water film is always present is critically important to this seal’s functionality, reliability and longevity.  Even though the film between the seal surfaces is minute, water moving through the seal and bellows ensures it remains present and, in the process, absorbs and removes heat.  Without it, these seals will quickly overheat and ultimately be ruined, which in turn leads to leakage.

ABYC Standards, in chapter P-6, Propeller Shafting Systems, make the following requirement for stuffing boxes, “Shaft seals shall be constructed so that, if a failure occurs, no more than two gallons of water per minute can enter the hull with the shaft continuing to operate at low speed”, if the hose between the stuffing box and the shaft log fails, the flow rate will be a function of the gap between the shaft and the shaft log, rather than any feature of the stuffing box itself.  If, however, the seal itself fails, then the flow rate will be dictated by the gap between the stuffing box body and the shaft.  It’s a question worth asking the the manufacturer of the dripless stuffing box you are considering using.   

Depending on the vessel’s speed, water injection can be obtained from a pressurized source, i.e. the engine’s raw water cooling circuit; from a forward-facing ram or scoop mounted to the hull; or it can simply be a passive “riser” that allows trapped air to escape, thereby ensuring the seal remains submersed.  The latter is typically used only aboard slow-moving, displacement power and sailing, vessels.  Above all else, the manufacturer’s specific instructions for providing water, or releasing air, must be followed.

As an illustration of its longevity, when working as a young mechanic, as part of a repower project, I installed a face seal stuffing box on a yacht club launch.  Years later I returned to visit my former workplace and decided to check on the engine as well as the seal.  I reviewed the installation and it appeared very much the same as it did when I  first installed it.  Later on I inquired with the yard manager, “So how has that dripless shaft seal [they were new at the time] held up?”  I asked.  “What seal?” was his reply, which spoke volumes; the seal had been neither serviced nor adjusted since it was first installed (all stuffing boxes, dripless and conventional, should be inspected regularly); the engine’s clock had just clicked over the 2000 hour mark.  Such long-lived performance is not unusual for properly installed face seals; exceptional longevity is among their most noteworthy attributes.

Fort twin screw applications, dual water injection enables one engine to supply water to both seals when operating on one engine.  The stuffing box shown here includes an optional second injection point, which is paralleled with the other shaft’s stuffing box.

This sort of reliability can only be achieved, however, if the installation follows the manufacturer’s instructions without deviation.  A few of the more frequently violated installation guidelines (in addition to the aforementioned absent double set screws) involve incorrect compression of the bellows, resulting in too much or too little tension between the seal faces, and either leakage or overheating.  If over compressed seals often overheat, and bellows over-ride their hose clamps, which can cause the former to chafe and leak.  In my experience, if a face seal leaks, the first temptation of  an installer, boat builder or vessel operator is to simply increase the tension, by further compressing the bellows, rather than attempting to deduce the actual cause of the leak, which is unlikely to be tension-related if the seal was installed properly to begin with.

Failing to provide enough slack in the water injection hose, allowing the seal to “float” freely, or using a hose that is too stiff, can also lead to chronic leakage.  While J2006 Marine Wet Exhaust hose works well for almost every other raw water application, it’s far too rigid for stuffing box water injection applications. Type B fuel, on the other hand, is both rugged and flexible and is well-suited to this role.  For the ultimate in flexibility and longevity silicone hose can be used, however, it kinks easily, and thus it must be routed with care.  Conventional PVC potable water hose should never be used for this application.

The hose used to supply water to the stuffing box must be flexible, however, PVC hose such as that used for potable water, shown here, should not be employed, as it lacks the necessary robustness for raw water use.

Another face seal installation issue worthy of mention is the relationship between the shaft and the shaft log, the tube through which the shaft passes.  If the shaft is not parallel with and centered in the log, the seal faces will lack concentric and/or parallel alignment, and as a result they will have difficulty achieving a reliable watertight seal.  I’ve encountered this scenario several times, and the stuffing box itself is often pointed to as the culprit, when in fact the problem lies with the original engine and shaft installation.  Some small, two and three cylinder engines can also challenge both face and lip seals alike.  Engines of this sort are known to vibrate considerably, especially at certain rpm ‘sour’ spots, and in doing so those oscillations are transmitted down the propeller shaft, which upsets the tension between the rotor and stator, or between lip and shaft, which in turn leads to leakage.  This problem is exacerbated by engines that are in poor tune.

Because face seals rely on external spring tension to maintain their watertight seal, they are susceptible to upset, which will result in leakage.  This can occur if gear, a wash bucket, fender or oar (all examples I’ve encountered), or misplaced foot, falls onto the bellows, dislodging the stator from the rotor, resulting in leakage. The effect is temporary, it lasts only as long as the object is resting on the stator.  Loose gear around a propeller shaft is never desirable, regardless of the stuffing box type (I once saw the result of an encounter between a shore power cord and a shaft, the latter bent, the engine was pulled off its mounts, and the vessel flooded before it could be hauled).  As a result of this upset susceptibility, my preference is for the installation of protection, in the form of a shelf or cover, over face seals.

Yet another method of achieving a drip-free seal involves the use of a lip seal.  Lip seals have been around for almost as long as internal combustion engines; they are used to seal crank and transmissions shafts, keeping oil in and dust out, as well as in a variety of other industrial applications.

Lip seals like the one shown here are self-centering, they rely on the interface between the lip and the spinning shaft to make a watertight seal.  The one shown here is equipped with a spare seal carrier, which retains and protects a set of replacement seals.

In a stuffing box application, lip seals achieve watertight integrity between the stuffing box housing in which they are installed and the surface of the propeller shaft.  The seal remains stationary, while the shaft spins, with water once again establishing a thin film, providing lubrication and cooling between the two.  For this reason, in order for such a seal to work, and much like the face seal, the shaft must be clean, smooth and free of all gouges, nicks, pitting or corrosion, at least in the comparatively small area where the seal will make contact.  A shaft whose surface is marred in almost any way is not a suitable candidate for a lip shaft seal, and unlike the face seal virtually any irregularities which cannot be polished away are too much. For after-market installations, shafts should be closely inspected for defects in the area where the seal will ride.  If no substantial issues are found, the surface should be, once again, cleaned according to the manufacturer’s instructions.

Prop shafts must be free of pitting or other irregularities where face seal O rings and especially lip seals reside, the latter are more sensitive to this issue.  If the surface is not smooth, it will be difficult to achieve a watertight seal. 

Lip seals frequently include an installation tool or hat; this is inserted between the shaft and seal during installation, which protects the seal from damage.  These should be retained for future use – any time the shaft is removed they are needed – they can be wire-tied near the stuffing box.  Don’t forget to remove the hat before the vessel is launched, if you fail to do so the seal will leak until it is removed.

Lip seal stuffing boxes typically rely on an integral support mechanism that’s not unlike a shaft bearing.  Made up of a synthetic material into which flutes or grooves have been cut to facilitate water flow, it centers and steadies the stuffing box on the shaft.  As a result, this type of seal tends to be somewhat less sensitive to misalignment between the shaft and shaft log.

Like face seals, lip seal stuffing boxes are reliant on cooling water to provide lubrication and cooling.  Unlike face seals, in most cases that water supply should be pressurized rather than passive, i.e. the seal must use an active water supply rather than a simple vent.  For all seals, the water injection flow rate, some manufacturers specify a required minimum flow rate, should be verified at the time of installation and again periodically thereafter.

The water injection hose must be flexible enough to allow the a dripless stuffing box to float, if it’s too rigid, or too short, it can side load the seal, causing it to leak.

Because of its small diameter, typically 3/8”, it’s not unusual for this supply to become clogged with silt or pieces from decaying zinc anodes located in heat exchangers (for this reason, some users prefer to tap water supplies  prior to the heat exchanger).  Being sensitive to, albeit to a lesser degree than face seals, side loading, lip seal injection hose must also be flexible, and it should of course meet the seal manufacturer’s requirements.  Like the face seal, lip seal stuffing boxes must be allowed to float freely, overly stiff hose or hose that leaves little or no slack will limit this necessary movement.  When installed properly, with some variance for shaft rpm, lip seals can be expected to provide upwards of a thousand hours of leak-free service.  Replacement of the lip seal in this type of stuffing box requires that the shaft be separated from its coupling.  While that doesn’t necessarily require hauling the vessel, it’s a task few do it yourselfers will undertake.  For that reason it’s desirable for spare seals, most installations include at least two, to be installed on the shaft, supported and protected by a proprietary carrier.  These seals can be replaced while the vessel is afloat.

Tides Marine, the manufacturer of the Tides SureSeal, the most common lip seal stuffing box available at the time this was written, does not recommend the use of their product on engines with less than four cylinders.  The reason for this caveat is the vibration inherent in one, two and three cylinder engines, which, at the right, or wrong, frequency can cause a momentary gap to develop between shaft and seal, which in turn will allow water to leak past the lip.  I’ve seen Tide seals used on small auxiliary sail engines with no issues, however, if you choose that route, and you have a leak issue, you’ll have no recourse with the manufacturer.

Keep the Heat Off

Regardless of which type of seal is used, temperature measurement remains the most accurate method of ensuring proper operation.  Like conventional stuffing boxes, dripless seals should not operate at a temperature that is greater than approximately 40°F above that of the water in which the vessel is operating.  While some seal manufacturers will technically approve of higher temperatures, in my experience such higher temperatures are often indicative of less than ideal water flow.  While all stuffing boxes require exposure to water to remain lubricated and cool, dripless seals are exceptionally sensitive to interruption of water flow, and the heat this produces.  This can occur if the water injection hose becomes clogged, as mentioned previously, if a vessel runs aground for instance, or if the stuffing box becomes air locked, which may occur when a vessel is launched; face seals should be bled or burped after each launching, and before the engine is placed in gear, to prevent this from occurring.

Temperature remains a valuable indicator of a seal’s functionality, if it’s significantly hotter than the water in which the vessel floats, it’s almost certainly not receiving enough flow.  If they get hot enough both lip and face seals will overheat, and fail, which will lead to leaking.

Variation on a Theme, Twin Screw

With one caveat, most twin screw installations, both lip and face seals should be equipped with parallel cooling water plumbing.  This arrangement ensures that, when operating on one engine, a free-wheeling shaft’s seal will remain lubricated and cool.  The caveat involves the method by which water is drained from the engines’ exhaust systems.  If portions of the exhaust are higher than the engine’s riser, then such a crossover method must include isolation valves to prevent flooding of the engine’s cylinders.  If you vessel is equipped with such a crossover (or requires one), make sure you or a professional review the exhaust system design to determine if such flooding, when operation on one engine, is a possibility.  Make certain as well you understand how these valves should be manipulated when operating on one engine (they should be labeled) and remember to open valves before once again operating normally, on two engines.

This bellows is over-compressed, so much so that it is over-riding its hose clamps, visible at the bottom of the image.  Over-compression is problematic in and of itself, however, the bellows can also be damaged as it chafes against a clamp.

Related to this issue is the subject of towing.  If a vessel is to be towed, in order to avoid stuffing box overheating, be absolutely certain to follow the protocol of the manufacturer.  On at least two occasions I’ve encountered dripless stiffing boxes that overheated and rotated with the shaft during relatively brief tows.  Shaft immobilization is typically not a practical alternative for most power vessels, the back-driving force created by the prop is substantial and often impossible to overcome on all but the smallest props.

Dripless stuffing boxes; both lip and face seals, have made the advent of a dry bilge a reality.  With less water in the bilge, corrosion and odors can be reduced, and with a normally dry bilge, any water that does make an appearance will, or should, immediately draw attention to itself.

I’ve installed, serviced and inspected hundreds of stuffing boxes of all types, conventional and dripless.  All work well provided they are installed properly and maintained in accordance with manufacturer instructions.  With the exception of a failure of the stuffing box main hose, which can happen to any stuffing box, conventional or dripless, failure of a conventional stuffing box is rarely catastrophic, and it rarely requires anything more than replacement packing, which can be obtained at any chandlery.  On one at-sea repair opportunity, I used strips of cut-up T shirt lubricated with cooking lard.

Most dripless stuffing boxes rely on a ultra-flexible hose to allow the sealing portion of the assembly to align to and “float” on the shaft.  If the shaft is not centered in the shaft log, or if the shaft vibrates excessively, leakage can result.

Because there’s no free lunch, dripless stuffing boxes are at a greater risk of catastrophic failure, and when they do fail or simply leak, proprietary parts are almost always needed, which can pose a challenge for those cruising remotely.  Those who fall into this category should carry vital spares; including the main hose, and spare seals, lip or face (conventional stuffing box users should of course carry packing material and replacement hose clamps).  Spare rubber parts should be stored in an airtight bag away from heat and ozone, the latter is harmful to rubber and plastic and is generated by electric motors, and of course ozone generators.  At least one dripless stuffing box manufacturers prohibits the use of ozone generators with their products, take heed to this warning, I’ve witnessed the damaging effects of these devices on rubber and plastic components.

If you yearn for the proverbial dusty bilge, a dripless stuffing box is likely the only way you will achieve this goal.  Make certain you, or whoever you entrust to install a dripless stuffing box, fully reads and understands the instructions, even if you, he or she has installed them in the past, as manufacturers update and change these guidelines.  Finally, make certain you also understand service intervals, particularly bellows replacement, which may be required after a given number of years, regardless of use.

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What You Should Know About Your Stuffing Box

The  stuffing box,  sometimes referred to as a  packing box  or a packing gland, has been around for many years; so many in fact, that some insist it was in use almost as far back as ancient mariners. We're not so sure about that, but regardless of the when, it is a well proven, reliable, and functional design. Most new boats since the year 2000 have shaft seals that require no packing, but sterndrive boats built before then have traditional stuffing boxes with packing.

The stuffing box is still an inexpensive method of sealing a rotating shaft when compared to the newer alternative system, especially in the larger sizes. A stuffing box does have some limitations, but so do many of the alternative shaft seals out there. One such limitation of the stuffing box is that it is not suitable for high-speed shafts.

This is not due to the stuffing box itself but rather the packing.  Stuffing box packing  has also seen its fair share of evolution and there are a few different choices out there, but they all have similar characteristics in common. The  stuffing box packing  is compressed to achieve the seal around the rotating shaft and the stationary housing. The sealing surface around the shaft is large and when the shaft turns, the surface friction creates undesirable heat.

This heat eventually deteriorates the surface of the shaft and reduces the effectiveness of the bearing packing. To mitigate the heat buildup, it is important to adjust the stuffing box correctly so that during operation some liquid passes by the seal to aid in lubricating the seal and reduce the heat buildup; and that when idle, no liquid passes by the seal. This can be done with constant attention, which is not always possible, and that leads to an annoying, constantly dripping shaft seal.

Aside from a lack of constant attention being a cause for stuffing box ineffective performance, other contributing factors are the condition of the shaft surface, the shaft alignment, and the condition of the bearings.  Interior shafting components such as the shaft coupling is also critical in ensuring that a shaft runs true. Shaft vibration, among other detriments, contributes to shaft sealing failure. Installing a flexible coupling reduces vibrations and can compensate for slight misalignment issues.

A stuffing box and the stuffing box packing will require maintenance, as the rubber hose will deteriorate over time and the propeller shaft seal will diminish as the packing wears out. Other hardware might need replacing as well, and thankfully there is still manufacturer support for even some of the oldest propeller shaft seals out there.

Alternatives to a shaft sealing with stuffing is a  dripless shaft seal.  There are a few types on the market with all achieving the same result--that being a dripless shaft seal. So, if a new stuffing box, shaft sealing, propeller shaft seal or other parts is on the maintenance list, take a look at what we have here for you at Go2marine.