Shaft seal replacement

[sailoppopotamus]

Thanks to everybody for your help so far. I was down at the boat again today and cleaned the shaft where the seal sat. Unfortunately, I the shaft is quite pitted. The pitting extends around 5cm in length. I thought that perhaps I might be able to get away with getting the shaft shortened so that the seal sits on a new part of the shaft but unfortunately this would put my propeller too close to the P-bracket. Is this somehow repairable or is it time for a new shaft?

 

[sailoppopotamus]

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

The shaft is worn, see the picture I posted above. Speedislavfe or some variation thereof may be a solution, otherwise it looks like I might need a new shaft.

 

[Plum]

Thanks to everybody for your help so far. I was down at the boat again today and cleaned the shaft where the seal sat. Unfortunately, I the shaft is quite pitted. The pitting extends around 5cm in length. I thought that perhaps I might be able to get away with getting the shaft shortened so that the seal sits on a new part of the shaft but unfortunately this would put my propeller too close to the P-bracket. Is this somehow repairable or is it time for a new shaft?

View attachment 147205

Inside the VP gland are two relevant parts. First there is the bearing part that is like a Cutless bearing then there are the two lip seals. I assume the pitted area is where the bearing part sits and if it has been laying static for a long time with oxygen excluded between the shaft and the bearing that will explain the pitting but I do not believe that that pitting will have much effect on the wear of the bearing part for which it's only function is to keep the lips seals concentric to the shaft. The part of the shaft where the lips run does not appear to have any grooves so don't see why they will not function correctly to keep the water out as long as they are greased.

Www.solocoastalsailing.co.uk

 

[Pete7]

The shaft is worn, see the picture I posted above. Speedislavfe or some variation thereof may be a solution, otherwise it looks like I might need a new shaft.

New 4ft shaft this summer with 1" diameter was £250 from Solent Propellers. They reckoned a repair would be similar so better to start again.

The Volvo is a good seal, needs little maintenance other than a sugar cube of grease once a year and good for about 7 years. However, for some strange reason needs Volvo grease. Previously I did try some Castrol and it dripped. Dried the boat on the slip, take it all apart then clean and back in again as the tide was coming in. Problem solved with the right grease. Make sure the lip seals face aft and when assembling. Volvo supply a plastic cup widget to protect them, keep it safe for future use.

 

[chewbacca]

Agree it does look badly pitted aft,not so much so where the seal is sitting, hard to tell from a photograph exactly you'll have a better idea and judge for yourself, it really has to be a polished unblemished surface. Is there enough in the coupling to push it out to the rear?If you decide to go down the new shaft route to give you a rough idea of price I paid £250 for a shaft last year just marginally over 1 metre in length. Supplied by silletts-sonic in Poole. Excellent service, advice on the phone, fast turnaround no connection just satisfied with the service and the shaft.
Regards

 

[sailoppopotamus]

Inside the VP gland are two relevant parts. First there is the bearing part that is like a Cutless bearing then there are the two lip seals. I assume the pitted area is where the bearing part sits and if it has been laying static for a long time with oxygen excluded between the shaft and the bearing that will explain the pitting but I do not believe that that pitting will have much effect on the wear of the bearing part for which it's only function is to keep the lips seals concentric to the shaft. The part of the shaft where the lips run does not appear to have any grooves so don't see why they will not function correctly to keep the water out as long as they are greased.

Www.solocoastalsailing.co.uk

Agree it does look badly pitted aft,not so much so where the seal is sitting, hard to tell from a photograph exactly you'll have a better idea and judge for yourself, it really has to be a polished unblemished surface. Is there enough in the coupling to push it out to the rear?If you decide to go down the new shaft route to give you a rough idea of price I paid £250 for a shaft last year just marginally over 1 metre in length. Supplied by silletts-sonic in Poole. Excellent service, advice on the phone, fast turnaround no connection just satisfied with the service and the shaft.
Regards

Looking at a cross-section of the Volvo seal that I found on the Internet (posted here for reference) it appears that you might be right and potentially saved me from buying a shaft. I'm not sure about how much shaft is in the coupling, I'll undo that soon to replace the rear seal of my Yanmar. At any rate it seems worth a shot to try with the existing shaft-- I can launch the boat with a new seal and see what happens. It looks like I have a decent chance that it will not. If it does, it doesn't look like it would be anything but a tiny leak, i.e. it's not going to sink the boat. Please feel free to comment if you think this is foolish -- it looks like a new shaft will set me back 300-400 euros, which I'd rather spend on other things if given the choice.

The Volvo is a good seal, needs little maintenance other than a sugar cube of grease once a year and good for about 7 years. However, for some strange reason needs Volvo grease. Volvo supply a plastic cup widget to protect them, keep it safe for future use.

The Volvo seal is made by Radice, who also make their own version of it. Apparently very similar designs, but with the addition of a vent that can be used to burp when refloating and a grease nipple to make greasing easier. I'm buying it for the latter feature.

 

[Plum]

The Volvo seal is made by Radice, who also make their own version of it. Apparently very similar designs, but with the addition of a vent that can be used to burp when refloating and a grease nipple to make greasing easier. I'm buying it for the latter feature.

I have the regular VP seal and find the greasing with a straw one per year so easy, particularly as you can ensure the grease gets spread around the shaft under both seals using the correct volume of grease (1 cc). If the Radice grease injection tube is between the two lips I don't see how the grease would get between the forward lip and the shaft, or how you would control the volume of grease getting to the lips if you are inserting it down a short tube first.

The little tube (toothpaste type) of VP grease has a nozzle that inserts in to a drinking straw. As you squeeze the tube of grease you can see the length of straw that gets filled with grease (you can calculate the length required for 1cc). The little tube of grease will last you more than 10 years!. Now flatten 20mm of the end of the tube so it is flat, slide that flat piece under the lips, moving it around as you slide your fingers along the straw to squeeze the grease out until it is all gone.

If you are on a drying mooring and you had to burp the seal every time you wanted to use the engine then, yes, the vent tube on the Radice version makes a lot of sense.

www.solocoastalsailing.co.uk

 

[sailoppopotamus]

If the Radice grease injection tube is between the two lips I don't see how the grease would get between the forward lip and the shaft, or how you would control the volume of grease getting to the lips if you are inserting it down a short tube first.

Are you sure you mean the forward lip, not the rear? Isn't the grease supposed to fill the area between the two lips? My inability to get my head round what many describe as such a simple task is what has led me to consider the Radice seal in the first place Incidentally, this is what Radice have to say about lubricating their seal:

Screw the tube of silicone grease into the specially provided attachment and squeeze it into
the seal, bearing in mind that there is enough grease in the tube for 4 or 5 applicatons.

I think the idea is that you just squeeze enough and it eventually goes everywhere.

Anyway, this got me thinking that perhaps I'm better off with a Volvo seal only because the lip placement may be slightly different in the Radice seal. I'll try to hunt down the dimensions of the parts, but with Radice there's the risk that the lips will land on the pitted area of my shaft. Unfortunately the existing seal I have is of unknown provenance, so perhaps it's not an identical copy of the Volvo seal either.

 

[chewbacca]

Agree Absolutely no harm trying a new seal on and like you've said it's not going to sink the boat but the volvo seal does need to be greased using the straw method. My understanding is the outer rearmost seal is lubricated by seawater along with the supporting bearing portion and the grease lubricates the innermost seal.
Regards

 

[Plum]

Are you sure you mean the forward lip, not the rear? Isn't the grease supposed to fill the area between the two lips?.

Yes I do mean the forward one. You need to get the grease between the lips and the shaft, particularly the forward one that probably does not get water to it. If you force grease between the two lips using the injection tube of the Radice seal,the aft lip will let the grease through but the foward one will just tighten against the shaft. The VP grease does not flow or run, it is very good at staying where you put it. Filling the gap between the two lips is, to me, a bad idea as the body of grease may be deflecting the aft lip. If you keep forcing more grease in you could block the vent tube of the Radice type.

www.solocoastalsailing.co.uk

 

[superheat6k]

I would suggest a PSS seal (pyi.com) but the O rIngs on the rotor must sit on a non pitted section of the shaft. Once you have identified the PSS part numbers ASAP Supplies can get the items required.

Looking at the photo in post 21 I would expect the PSS rotor would sit further forward on the clean area of the shaft.

This is the listing for 25mm shaft x 1 3/4" (43mm). Note the 1" (25.4mm) has a different listing so you will need an accurate shaft measurement. On a boat below 12 knots you do not need the cooling water supply.

Propeller Shaft Seal 25mm PSS Hi Speed

 

[Lightwave395]

I would suggest a PSS seal (pyi.com) but the O rIngs on the rotor must sit on a non pitted section of the shaft. Once you have identified the PSS part numbers ASAP Supplies can get the items required.

Looking at the photo in post 21 I would expect the PSS rotor would sit further forward on the clean area of the shaft.

I replaced a Radice seal with a PSS, the 'O' rings sit quite a way forward of where the end of the Radice seal was. It's expensive but very good

 

[Tranona]

I replaced a Radice seal with a PSS, the 'O' rings sit quite a way forward of where the end of the Radice seal was. It's expensive but very good

A PSS is over 3 times the price of a Radice (and much the same as a new shaft!). However there is no need to change the shaft because the pitting is inside the fluted bearing - the seems to be no wear in the area where the lip seals sit. The OPs problem is leakage round where the stern tube is bonded into the hull, not the seal. Straight replacement of the shaft seal for under £100 is the way to go. It was original equipment on the boat 30 years ago. No need to change type of seal.

 

[sailoppopotamus]

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.

The OPs problem is leakage round where the stern tube is bonded into the hull, not the seal. Straight replacement of the shaft seal for under £100 is the way to go. It was original equipment on the boat 30 years ago. No need to change type of seal.

What makes you think it's around the stern tube? I had just discounted this very unpleasant scenario on the basis that water didn't seem to leak when the boat was stationary. Getting a new stern tube in there is beyond my own fiberglassing skills so I'd have to pay the yard quite a bit of money and hope they do the job properly.

 

[Tranona]

Sorry if I have misinterpreted your original photos, but there is a lot of staining underneath where the tube exits from the hull and deposits on the bottom of the seal where it meets the joint between the GRP and the tube. This suggests there has been a weep there for some time, either between the tube and the GRP or because the clamp was not tight enough. might be worth putting a bead of sealant around the tube where it enters the GRP. Let it cure so it forms a sort of gasket before you replace the seal.

 

[dankilb]

Is the logic for a new seal either a) to renew and upgrade to a vented type or b) ‘diagnosis by replacement’ for the leak?

If the latter, I’d be surprised if a new seal cures the leak. Unless it wasn’t clamped properly, these (dripless) seals rarely leak.

 

[Tranona]

Makes sense while it is all apart to replace it with a Radice to get the benefit of easier greasing and the air vent to remove the need for burping.

 

[sailoppopotamus]

Is the logic for a new seal either a) to renew and upgrade to a vented type or b) ‘diagnosis by replacement’ for the leak?

If the latter, I’d be surprised if a new seal cures the leak. Unless it wasn’t clamped properly, these (dripless) seals rarely leak.

I'll be honest and go for (b). I had a leak, and not knowing how old the seal is, I assumed it was due for replacement. Only after removing the seal did it occur to me that the leak might be from the stern tube. I guess if I can fix that with some sealant then it's only a minor inconvenience -- any suggestions as to what sealant?

Meanwhile I've spent the last day educating myself on the subject of shafts, couplings and seals. First, I'm worried that the pitting on the shaft may be crevice corrosion; it also seems that I should check the condition of the shaft in the cutlass bearing, as it is likely to be in bad shape there as well. To replace the seal I'll have to remove the shaft from the coupling. I've been reading this terrifying but seemingly well informed article which suggests I'll likely need to replace the shaft coupling as well, since the current one is unlikely to provide a proper interference fit once/if I manage to break it loose. Regardless of whether I replace the shaft it seems I'll have to remove it from the boat to check for straightness and get it to a machine shop for to be "fitted and faced" to the shaft. And only this morning I came to the realisation that removing the axis from the boat might entail dropping the rudder, which in turn requires the boat to be lifted as the yard won't allow digging.

In short, I'm stressing over this and overthinking everything. I'll try to get down to the boat tomorrow to disconnect the coupling from the transmission and remove the prop, to see if there's any chance of getting the shaft past the rudder.

I'd like to thank everyone for your help so far. I'll keep updating this thread and documenting my progress in the hope that it will be useful to others undertaking similar work.

 

[vyv_cox]

I'll be honest and go for (b). I had a leak, and not knowing how old the seal is, I assumed it was due for replacement. Only after removing the seal did it occur to me that the leak might be from the stern tube. I guess if I can fix that with some sealant then it's only a minor inconvenience -- any suggestions as to what sealant?

Meanwhile I've spent the last day educating myself on the subject of shafts, couplings and seals. First, I'm worried that the pitting on the shaft may be crevice corrosion; it also seems that I should check the condition of the shaft in the cutlass bearing, as it is likely to be in bad shape there as well. To replace the seal I'll have to remove the shaft from the coupling. I've been reading this terrifying but seemingly well informed article which suggests I'll likely need to replace the shaft coupling as well, since the current one is unlikely to provide a proper interference fit once/if I manage to break it loose. Regardless of whether I replace the shaft it seems I'll have to remove it from the boat to check for straightness and get it to a machine shop for to be "fitted and faced" to the shaft. And only this morning I came to the realisation that removing the axis from the boat might entail dropping the rudder, which in turn requires the boat to be lifted as the yard won't allow digging.

In short, I'm stressing over this and overthinking everything. I'll try to get down to the boat tomorrow to disconnect the coupling from the transmission and remove the prop, to see if there's any chance of getting the shaft past the rudder.

I'd like to thank everyone for your help so far. I'll keep updating this thread and documenting my progress in the hope that it will be useful to others undertaking similar work.

I disagree that most couplings are an interference fit on the shaft. This would require the coupling to be heated to fit it, which I believe is most unusual. Check my website Coupling types and removal I doubt than any shown here are an interference fit, mostly they have a pinch fit.

 

[sailoppopotamus]

I disagree that most couplings are an interference fit on the shaft. This would require the coupling to be heated to fit it, which I believe is most unusual. Check my website Coupling types and removal I doubt than any shown here are an interference fit, mostly they have a pinch fit.

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.