Shaft seal replacement

[sailoppopotamus]

Last year I bought a Jeanneau Sun Light 30 which has a shaft/p-bracket arrangement. My bilges were completely dry for the first year. During haul out, I swapped out the fixed prop for a 2-bladed Flexofold, and also replaced the cutlass bearing using something similar to this tool - it had some play, was of unknown age, and I had the prop off anyway so why not. I did not realign the engine after this.

I then relaunched the boat, and spent a few months cruising about this summer. Quite soon, I noticed that my bilge was no longer dry, and I could find some salt water in the stern where the shaft exits the boat. I have a no-name Volvo seal of unknown age, so this is not supposed to happen. I kept an eye on it and it was never too dramatic. It only seemed to leak when motoring. My engine does vibrate quite a bit, even without the prop engaged.

The boat is now out of the water. My engine mounts are due for replacement, so I'll have to realign the engine anyway this year, and I want to replace the shaft seal to stop the leak. My intention was to replace with a Radice seal, to make greasing easier. However upon pulling the old seal I discovered the following:

A. My stern tube appears to be 43.7 - 44mm (my Vernier caliper skills are lacking). This seems completely non-standard for my 25mm prop shaft.
B. I can see quite a lot of salt at the bottom of the stern tube, and at the bottom part of the old seal (see pictures; I twisted the seal to break it loose from the stern tube, the salty bit of the seal was its lowest part when I installed it).

I'm a bit unsure as to how to proceed. I'm troubled by two things:

1. Is it possible that the seal was fine all along and that the water ingress was actually from the hull-stern tube joint? Is there anyway of knowing whether this joint is leaking rather than the seal itself?

2. What do I do about the non-standard stern tube size? Max stern tube size for Volvo and Radice 25mm shaft seals is 42mm. Would a 42mm shaft seal work with the 44mm stern tube, or would it be stupid to attempt this?

 

[Stemar]

A couple of observations

There are drops of water on the seal and on the pipe next to it in the first pic. Is is possible that the water's coming from somewhere else?

Secondly, there are signs of wear on the shaft in the last pic. If this is where the seal rubs, that could cause slight weeping and, if that is the cause, a new seal that rubs in the same place is unlikely to fix it.. When I changed the seal on my last boat, it was a fair bit worse than that, so I went with a PSS seal as the wearing surface is built into the seal.

 

[dankilb]

The 'shaft log' (believe that's the technical term - as 'stern tube' generally denotes having a bearing inside...?!) looks to be in decent condition. I definitely agree with Stemar that a leak is likely to be somewhere else.

But...! We have a Jeanneau with a similar setup and our shaft log was essentially found to have failed when we bought the boat. The metal had dezincified and turned pink. A big chunk of the bottom of the hose tail crumbled away in my hands! Had our boat been launched like this, it would definitely have leaked (and quite possibly sunk the boat).

So, it may be worth further exploration. If it's like our boat and that area is its own little 'bilge' - could you refit the seal and fill it with water, then see if any leaks out of the boat? I appreciate that may be unlikely, factoring in water pressure and vibration in actual use - but you never know. Either way, I would treat that fitting to proper inspection. I'm not sure why it appears the glass has been ground/sanded on top? That glass matt there doesn't look like what I'd personally recognise as Jeanneau factory (they used a blue-green coloured resin on ours and almost always woven roving above any CSM on the inside of our layup). Maybe it's been repaired before?

Here's the repair that we completed on ours (I 'sheaved' the old log, to avoid having to mechanically remove it from the boat, by glassing in a composite Tru Design fitting, slightly modified and encapsulated in biax cloth/epoxy layup - the brass bearing was used to align the shaft with the engine/p-bracket):

 

[sailoppopotamus]

A couple of observations

There are drops of water on the seal and on the pipe next to it in the first pic. Is is possible that the water's coming from somewhere else?

Secondly, there are signs of wear on the shaft in the last pic. If this is where the seal rubs, that could cause slight weeping and, if that is the cause, a new seal that rubs in the same place is unlikely to fix it.. When I changed the seal on my last boat, it was a fair bit worse than that, so I went with a PSS seal as the wearing surface is built into the seal.

I think what happened is that water still trapped in the seal splashed about as I removed it. I'm pretty sure that's where the water is coming from. The only other place seawater could get in the boat in that area is the rudder post, but paper towels placed around it have remained completely dry. As for the wear, is this something that a machine shop could fix or is a new shaft on the horizon? The PSS is indeed an option, albeit a very expensive one.

The 'shaft log' (believe that's the technical term - as 'stern tube' generally denotes having a bearing inside...?!) looks to be in decent condition. I definitely agree with Stemar that a leak is likely to be somewhere else.

But...! We have a Jeanneau with a similar setup and our shaft log was essentially found to have failed when we bought the boat. The metal had dezincified and turned pink. A big chunk of the bottom of the hose tail crumbled away in my hands! Had our boat been launched like this, it would definitely have leaked (and quite possibly sunk the boat).

So, it may be worth further exploration. If it's like our boat and that area is its own little 'bilge' - could you refit the seal and fill it with water, then see if any leaks out of the boat? I appreciate that may be unlikely, factoring in water pressure and vibration in actual use - but you never know. Either way, I would treat that fitting to proper inspection. I'm not sure why it appears the glass has been ground/sanded on top? That glass matt there doesn't look like what I'd personally recognise as Jeanneau factory (they used a blue-green coloured resin on ours and almost always woven roving above any CSM on the inside of our layup). Maybe it's been repaired before?

Here's the repair that we completed on ours (I 'sheaved' the old log, to avoid having to mechanically remove it from the boat, by glassing in a composite Tru Design fitting, slightly modified and encapsulated in biax cloth/epoxy layup - the brass bearing was used to align the shaft with the engine/p-bracket):

Thanks for correcting me on the terminology, was not aware of the distinction. It doesn't look original, I don't know about Jeanneau's fiberglassing but I don't see why they would ground/sand it as you say. I don't think your leak trick would work -- it only leaked when the boat moved, and the leak was very slight anyway so I wouldn't be able to tell if it's leaking outside the boat or merely evaporating. What does a 'proper' inspection of the stern log involve?

Your repair job is beautiful, I'm envious!

 

[dankilb]

What does a 'proper' inspection of the stern log involve?

There are others on here with proper expertise in metallurgy, boatbuilding and generally diagnosing these things - I'm more at the 'fix what's obviously broke' level myself! But I'd guess you might want to check things like - any sign of the metal going pink or powdery (dezincification); tapping/sounding the bits you can access, to check no specific areas sound noticeably 'dull'; potentially removing the shaft to have a better visual inspection inside (for cracks, pinkness, etc.); and looking for any signs of cracks/weepage outside the hull in the fibreglass around the shaft log.

I don't know for sure, but my guess is that our 'shaft logs' involve something like this fully encapsulated in glass (so ignore the screw holes - just a random image from the internet!) to form part of the hull structure:

...so that gives a potential idea about where water could leak in. I'd say there aren't many options for water to get in at all - but if it did, it would either suggest a failure in the glasswork holding it in place or a failure like we encountered in part of the metal fitting itself.

 

[dankilb]

...this is another good illustration/example of the 'pinkness' associated with a failure of the log:

Repack A Stuffing Box

The above article hadn't been published when we encountered the same problem and it's the closest example I've seen...

Of course, yours looks nothing like that - which is good news all round!

 

[penfold]

I doubt it looks like that; more likely to just be a brass tube glassed into position.

As for the wear, is this something that a machine shop could fix or is a new shaft on the horizon? The PSS is indeed an option, albeit a very expensive one.

Clean this section with a green pot scourer; after that can you feel a ridge with your finger nail? If so it's worn out at that point; if the shaft or seal can be moved to place the seal lips on an unworn section of shaft then no worries, if not then it's new shaft time.

 

[vyv_cox]

There is a photo of a badly dezincified stern tube at Brasses and bronzes.

Corrosion is taking place from the inside to outside, which means replacement is the only option if it is this bad. As said above, it is probably only a brass tube glassed in, not expensive to buy but tricky to replace.

 

[sailoppopotamus]

It's a big job to replace the tube, and I think that the boat would leak constantly (not just when motoring) if that were the cause of the water ingress. I'll inspect it more carefully next time I'm at the boat but I think for the time being I won't attempt to dig it out of there. After all it seems to be in pretty good condition. So that leaves me with two problems:

1. The potential wear on the shaft. I'll clean and try to assess the wear with my fingers. Perhaps take it to a machine shop anyway, to have the shaft checked for straightness and get it lapped to the prop hub while I'm at it. How much wear is too much wear?

2. Finding a seal to accommodate my (seemingly randomly sized) 44mm tube. I'll clean this as best I can (vinegar?) just in case muck and crud are throwing off my measurements, but for the time being I'm operating under the assumption that it is indeed 44mm. I would prefer a lip seal to a face seal, but it seems that nobody makes a lip seal for a 44m tube. Perhaps I can get a 42mm Radice seal to fit over it, but I'm unsure as to whether this is possible to begin with, or what impact it might have on the seal's longevity.

 

[dankilb]

I’d be amazed if something like this (Radice copy - I have one and must say don’t think it’s as good as the real thing) wouldn’t fit: Stuffing Box Seal with Vent Pipe for 25mm Volvo Penta Prop Shaft

Advertised at 43mm. So surely your <1mm difference would be ‘within tolerance’ for a rubber seal of that size.

I’d guess the same would be true of the real Radice, in that it could be made to fit (with care).

It’d be an expensive mistake to make though, if it doesn’t fit or solve the leak, and perhaps not the best route to fault find.

So I defer to the resident engineers…

Good luck!

 

[dankilb]

As a practical suggestion, a couple of cm-wide slice cut from a small yoghurt pot or similar could help as a ‘bearing’ to protect the seal when sliding it over the log. Similar to the gadget they supply to protect the lip seal when sliding on the shaft. Lubed liberally with washing up liquid. It could be pulled out once the seal is partly on/safely over the edge.

And/or, I’m sure you could carefully remove 1mm from the OD of the log tail, using a strip of wet/dry paper, and working only on the very first few mm of the tube (to create a smoother and slightly thinner ‘bevel’ to the end of the tube).

Again, whether a critical part like this should be ‘encouraged’ - by whatever methods - over a slightly oversized fitting is another question altogether, of course!

 

[Keith-i]

44mm sounds very close to imperial 1.75" so probably is a standard size for tube. Have you looked at Lasdrop Gen 2 seals. I have one and thint it is very good.

 

[sailoppopotamus]

I’d be amazed if something like this (Radice copy - I have one and must say don’t think it’s as good as the real thing) wouldn’t fit: Stuffing Box Seal with Vent Pipe for 25mm Volvo Penta Prop Shaft

Advertised at 43mm. So surely your <1mm difference would be ‘within tolerance’ for a rubber seal of that size.

I’d guess the same would be true of the real Radice, in that it could be made to fit (with care).

It’d be an expensive mistake to make though, if it doesn’t fit or solve the leak, and perhaps not the best route to fault find.

So I defer to the resident engineers…

Good luck!

Thanks for the tip and links. I've been looking only at 'brand name' seals given the importance of the part but perhaps it's better to have a less famous but better fitting brand.

44mm sounds very close to imperial 1.75" so probably is a standard size for tube. Have you looked at Lasdrop Gen 2 seals. I have one and thint it is very good.

Thanks, I've been looking at their EliteSeal which looks pretty good. There aren't many reviews/mentions of it in forums, but the company has been around for a while so they can't be too bad. Not sure how relevant the 1mm is, perhaps it would be worth contacting them over it. Their seals are quite expensive though, and I'm not sure where to find them in Europe.

 

[Keith-i]

Their seals are quite expensive though, and I'm not sure where to find them in Europe.

I got mine from phmarine.co.uk

 

[penfold]

1. The potential wear on the shaft. I'll clean and try to assess the wear with my fingers. Perhaps take it to a machine shop anyway, to have the shaft checked for straightness and get it lapped to the prop hub while I'm at it. How much wear is too much wear?

Being able to feel it distinctly with your nail is too much wear.

 

[Tranona]

Pretty sure all the Volvo type seals are the same size (Radice actually make the Volvo one as well as their own version) so a new one will fit. The best alternative lip seal is the Tides Series One lakesterngear.co.uk/catalogue.pdf#page=37 which has a wider range of attachment diameters (1 5/8" and 1 3/4") but it is twice the price.

Think you are safe going with a Radice, but have the shaft cleaned and checked. the scuffing around the location of the lip seals is common and hopefully not deep enough to be a problem. A Face seal would mean that it does not run on the shaft, but will cost more than a new shaft and Radice seal!

 

[Poey50]

The Radice seal is actually a bit softer than the original Volvo seal and will stretch especially if warmed in hot water to start with. My nominally 42 mm Radice stretched to fit 44.45 mm and I've had no problem with it. Are you sure, though, that your shaft is 25 mm and not 1 inch? That seems to be the more critical dimension.

 

[vic008]

Then if the shaft is worn how about fitting a speedisleeve?

 

[chewbacca]

If the shaft is worn where the seal sits move it inboard slightly so the seal sits on fresh metal. I've found the volvo seals to be highly reliable and as long as they're lubricated, once a year, they perform very well. As mentioned measure the shaft to make sure if it's 1"or 25mm and if it's a genuine volvo seal the number is embossed on the side of the seal cross reference to make sure it's the correct one. I'd be tempted to replace like for like while it's out of the water, maybe that's just me. I think the 2mm diameter difference in stern tube diameter hasnt been an issue with the present seal and Id be happy to fit a new seal to it as it is now.
Regards

 

[sailoppopotamus]

The Radice seal is actually a bit softer than the original Volvo seal and will stretch especially if warmed in hot water to start with. My nominally 42 mm Radice stretched to fit 44.45 mm and I've had no problem with it. Are you sure, though, that your shaft is 25 mm and not 1 inch? That seems to be the more critical dimension.

I'm sure the shaft is 25mm. Thanks for sharing your experience, that's extremely useful to know. I've measured the tube and make it to be 43.7mm, so if you got yours to work I should have no problem with mine.

I'd be tempted to replace like for like while it's out of the water, maybe that's just me. I think the 2mm diameter difference in stern tube diameter hasnt been an issue with the present seal and Id be happy to fit a new seal to it as it is now.
Regards

This is a good point, however I would much prefer the radice to make the annual greasing easier. I'm not very reassured by the straw method for the Volvo seal. Unfortunately I don't know if it's an original Volvo seal, it doesn't say Volvo anywhere on it.