Shaft seal replacement

[Poey50]

A pinch fit is presumably when it's just held by virtue of being squeezed enough? I noticed the Yanmar on your website -- I have a Yanmar too (2GM20F with a Kanzaki KM2P), so perhaps I'm lucky in that regard. Or unlucky, as knowing this now I'll just worry that the shaft will fall off one day. Not sure about my particular coupling, will check tomorrow when I'm at the boat.

I have a split-halves Yanmar-type coupling. I have a particular screwdriver that is shallowly tapered along its length. With the bolts completely removed I tap the screwdriver into one of the splits. The shaft then slides out by hand. When refitting ensure you are using 8.8 high tensile bolts and torque them to the correct setting. I degrease and roughen the end of the shaft before fitting and also put my shaft anode 12 mm forward of the P-bracket as a final belt-and-braces.

 

[superheat6k]

I am aware of the PSS seal. While I'm sure it's a quality product and know that there are thousands of problem-free installations of it, I'm personally not comfortable with the potential risk of catastrophic failure with face seals. So I would prefer a lip seal, even if in the end it turns out to be more expensive.

I think you are over thinking the potential problems with what is likely the best shaft seal on the market.

 

[vyv_cox]

A pinch fit is presumably when it's just held by virtue of being squeezed enough? I noticed the Yanmar on your website -- I have a Yanmar too (2GM20F with a Kanzaki KM2P), so perhaps I'm lucky in that regard. Or unlucky, as knowing this now I'll just worry that the shaft will fall off one day. Not sure about my particular coupling, will check tomorrow when I'm at the boat.

I have a Yanmar 3GM30F with the same gearbox. There has never been a suggestion that the coupling has slipped or fallen off. I suspect you are worrying about a highly unlikely event.

 

[penfold]

A pinch fit is presumably when it's just held by virtue of being squeezed enough? I noticed the Yanmar on your website -- I have a Yanmar too (2GM20F with a Kanzaki KM2P), so perhaps I'm lucky in that regard. Or unlucky, as knowing this now I'll just worry that the shaft will fall off one day. Not sure about my particular coupling, will check tomorrow when I'm at the boat.

Not very likely, but if it's keeping you up at night fit a jubilee clip to the shaft beside the coupling; if it ever comes out the clip will stop the shaft falling out of the stern tube. Alternatively if your installation has a P bracket fit a shaft anode an inch or so forward of the P bracket which will serve the same purpose.

 

[Tranona]

I think you are over thinking the potential problems with what is likely the best shaft seal on the market.

The overthinking is in whether there is any need to change the seal at all. The Volvo type seal is simple, idiot proof and does the job - which is why thousands of Jeanneaus (and Beneteaus) have been fitted with them as OE for the last 30 years. The PSS is expensive, complicated and is not without its own potential problems which is perhaps why no volume manufacturer fits them as OE.

 

[sailoppopotamus]

I don't want this to turn into the shaft seal equivalent of an anchor thread, which is why I've tried to highlight my choice of a lip seal as the product of my own paranoid thinking rather than some universally accepted truth. I, who have no expertise on the matter, instinctively trust a lip seal more than a face seal, so I'll go for that. I'm sure the PSS seal is seaworthy, I just don't want to switch to it if I can reasonably avoid it. My comments about worrying that my shaft might slip away were partly in jest, but as I do have a p-bracket arrangement I'll nevertheless make sure my anode is as close forward of the p-bracket as is permissible. If worst comes to worst it's a last line of defence.

 

[Stemar]

I would very much have preferred to fit a Radice seal to Jissel - the job, including a new shaft, probably wouldn't have been much more than the PSS seal on its own, but to remove the prop shaft, either the rudder or the engine has to come out, neither of which is straightforward on a Snapdragon 24.

 

[sailoppopotamus]

So I managed to disconnect the coupling from the engine, disconnect the shaft from it (more on this in a bit) and pull the shaft back to examine the bit under the cutlass bearing. Some wear, but to me completely untrained eye seems rather superficial and not something that would compromise the integrity of the shaft.



More on the shaft coupling: Turns out I had a split coupling. Even though all the coupling has a fifth, threaded, hole for a grub screw, none was mounted. I did spot a circular dimple on the shaft, so evidently whoever had pulled the shaft previously to replace the lip seal had not bothered with putting the grub screw back in. What worries me is that the shaft easily slid off the coupling after I had undone the four bolts. I measured the ID of the coupling to be 25.2mm, the shaft being 25mm. Presumably this means the shaft coupling is completely shot (it's quite rusty) and must be replaced. There was no key or keyway.



All lin all, I think I'm keeping the shaft in the boat. It's quite a process to remove, as I have to drop the rudder, and, due to yard restrictions, it won't be possible to do that before April at the earliest. This also means I can't get a shaft coupling faced to it -- it's not clear how necessary this is if I get a new coupling but I think I'll just have to hope for the best. The pitting I originally noted in the thread still concerns me, but I want to wrap up this job now not in April.

My plan is to find a new split coupling, gently cleanup as much rust as I can on the transmission face plate with vinegar and a scotch brite, replace the seal for the Radice one and put everything back together. Do I get the new shaft coupling from Yanmar, or some other source? Do I have to align the existing dimple in the shaft with the hole in the new split coupling, or is it fine if I use a new location on the shaft? Should I reuse the existing A2 bolts or replace with 88-grade steel as has been suggested earlier in this thread? Finally, any ideas for sealing the stern tube, just in case the leak was from there?

Meanwhile I'll get started on replacing the engine's rear oil seal now that I have plenty of space to work with Thanks again to everyone for your help.

 

[Poey50]

What worries me is that the shaft easily slid off the coupling after I had undone the four bolts. I measured the ID of the coupling to be 25.2mm, the shaft being 25mm. Presumably this means the shaft coupling is completely shot (it's quite rusty) and must be replaced. There was no key or keyway.

I suspect you originally had a 1 inch shaft and the coupling is sized for that.

 

[Plum]

So I managed to disconnect the coupling from the engine, disconnect the shaft from it (more on this in a bit) and pull the shaft back to examine the bit under the cutlass bearing. Some wear, but to me completely untrained eye seems rather superficial and not something that would compromise the integrity of the shaft.

View attachment 147330View attachment 147331

More on the shaft coupling: Turns out I had a split coupling. Even though all the coupling has a fifth, threaded, hole for a grub screw, none was mounted. I did spot a circular dimple on the shaft, so evidently whoever had pulled the shaft previously to replace the lip seal had not bothered with putting the grub screw back in. What worries me is that the shaft easily slid off the coupling after I had undone the four bolts. I measured the ID of the coupling to be 25.2mm, the shaft being 25mm. Presumably this means the shaft coupling is completely shot (it's quite rusty) and must be replaced. There was no key or keyway.

View attachment 147333View attachment 147335View attachment 147329

All lin all, I think I'm keeping the shaft in the boat. It's quite a process to remove, as I have to drop the rudder, and, due to yard restrictions, it won't be possible to do that before April at the earliest. This also means I can't get a shaft coupling faced to it -- it's not clear how necessary this is if I get a new coupling but I think I'll just have to hope for the best. The pitting I originally noted in the thread still concerns me, but I want to wrap up this job now not in April.

My plan is to find a new split coupling, gently cleanup as much rust as I can on the transmission face plate with vinegar and a scotch brite, replace the seal for the Radice one and put everything back together. Do I get the new shaft coupling from Yanmar, or some other source? Do I have to align the existing dimple in the shaft with the hole in the new split coupling, or is it fine if I use a new location on the shaft? Should I reuse the existing A2 bolts or replace with 88-grade steel as has been suggested earlier in this thread? Finally, any ideas for sealing the stern tube, just in case the leak was from there?

Meanwhile I'll get started on replacing the engine's rear oil seal now that I have plenty of space to work with Thanks again to everyone for your help.

If that split coupling has never lost its grip on the shaft over the years it has been on there, why do you suspect it is "shot"?. Degrease, paint, refit with 8.8 bolts tightened to spec. Same goes for the flange bolts too. I would ever use A2 stainless fastenings for this. Fit the grub screw if it makes you feel any better.

www.solocoastalsailing.co.uk

 

[sailoppopotamus]

I suspect you originally had a 1 inch shaft and the coupling is sized for that.

Possibly but I don't think so. Everything else on the boat is metric, 25.2mm seems far too small for a 1 inch shaft. Either way, it is what it is.

If that split coupling has never lost its grip on the shaft over the years it has been on there, why do you suspect it is "shot"?. Degrease, paint, refit with 8.8 bolts tightened to spec. Same goes for the flange bolts too. I would ever use A2 stainless fastenings for this. Fit the grub screw if it makes you feel any better.

www.solocoastalsailing.co.uk

This guy argues that A “clearance-fit“, where the coupling just slides on is 150% unacceptable for a straight or even a split coupling. His argument is that the coupling should be replaced because the coupling rusts before the shaft, giving up material and compromising the fit. I have an old shaft, old coupling, no keyway so I'm trying to do my best to get the job as best I can under the circumstances. Thanks for the advice on the bolts, I'll take it -- for what it's worth the current bolts were 6mm Allen bolts, no nut, which didn't inspire much confidence either.

 

[Plum]

I measured the ID of the coupling to be 25.2mm, the shaft being 25mm.

Did you measure the bore of the coupling at the split end or the flange end? With all due respect, you did say in your post #1 that you were uncertain about your skill with a vernier caliper.

 

[sailoppopotamus]

Did you measure the bore of the coupling at the split end or the flange end? With all due respect, you did say in your post #1 that you were uncertain about your skill with a vernier caliper.

No offence taken, I measured at the split end; the calipers were not long enough to get into the flange end. Either way the shaft just slid off easily, whereas I read that most people typically struggle with pullers and blowtorches.

 

[Plum]

Possibly but I don't think so. Everything else on the boat is metric, 25.2mm seems far too small for a 1 inch shaft. Either way, it is what it is.



This guy argues that A “clearance-fit“, where the coupling just slides on is 150% unacceptable for a straight or even a split coupling. His argument is that the coupling should be replaced because the coupling rusts before the shaft, giving up material and compromising the fit. I have an old shaft, old coupling, no keyway so I'm trying to do my best to get the job as best I can under the circumstances. Thanks for the advice on the bolts, I'll take it -- for what it's worth the current bolts were 6mm Allen bolts, no nut, which didn't inspire much confidence either.

Then your "guy" and I disagree. A split coupling does not need to be an interference fit, and if it was, how would you get it onto the shaft?

 

[Poey50]

Possibly but I don't think so. Everything else on the boat is metric, 25.2mm seems far too small for a 1 inch shaft.

1 inch is 25.4 mm. My one inch split halves coupling has to be opened with a wedge in one of the splits to slide in the shaft. So 25.2 looks about right for 1 inch.

 

[Tranona]

You are right that it is all metric. Just clean it up and put it back together. As Plum says if you feel insecure put a grub screw in, but if you tighten the bolts correctly you will have no problems. there are thousands of these Yanmar couplings in use without any problems.

 

[Lightwave395]

I went with two grubs screws and drilled shaft indents to suit on my 3YM30 coupling, as per the saga here:

Make sure your nuts are done up very tight - Salutory note with a dash of puckering on the side

 

[vyv_cox]

Then your "guy" and I disagree. A split coupling does not need to be an interference fit, and if it was, how would you get it onto the shaft?

As I said 20 posts ago. An interference fit would be almost impossible to apply.

 

[Beneteau381]

I doubt it looks like that; more likely to just be a brass tube glassed into position.
View attachment 147120

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.

The seals have a ridged bearing surface with two lip seals, you can see where the ridged bearing has been touching the shaft, along with the two "wear" marks from the lip seals just inside and below your red circle, looks ok and normal to me, just polish with a scotch pad scourer

 

[Boater Sam]

, whereas I read that most people typically struggle with pullers and blowtorches.

Not in my experience, split couplings slide off easily with a wedge in the gap, that is how they are designed.