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Stern Tube Leaking


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Hi, having sorted my battery problems for the time being, I now have a leaking stern gland - a fairly constant drip when cruising.  I have put silicone grease in the small hole at the top every 100 hours as advised so think it must be something else. Any ideas?

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You will probably find a new gland is required. If the existing gland has worn a little part of your prop shaft down you might also find a new Vetus unit will leak. I fitted a shorter unit to a friends boat so the new gland ran on a new section of prop shaft. I think it was a Radice gland. Plenty of information on this site from Catweasel and also on Google.

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Check all of the mountings on the engine & gearbox are tight - there is usually a nut above and below the mounting feet - if the nut underneath comes loose you may not notice, and this will allow the engine to move out of alignment and increase wear on the stern gland. If applicable check that the mounting feet are securely attached to their location on the engine & gearbox

 

springy 

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38 minutes ago, Nick D said:

It's difficult to tell by the eye. Is there an easy way to find out?

How easily does the shaft turn by hand in neutral? Another crude method is to stand above and put the engine into gear, close one eye and see how much the shaft moves in from side to side or appears to wobble. That wouldn't identify any vertical movement of course. Ideally you'd use a needle gauge. Having said that your gland is flexible so it can take some misalignment.

I assume you're using the thick silicone grease? There is another thin grade. Anyway, instead of just putting a fingerfull of silicone grease into the hole at the top I undid the 3 screws holding on the front of the bronze housing, slid the front of the housing up the shaft and pushed a load of silicone grease in there. Be careful you don't break the gasket as you separate the housing. Water will come in at a rate of about 1 litre/minute so have your grease ready! This might also help to shift any grit in there that's causing wear and contributing to the leak.

If that doesn't work you could try loosening the coupling that holds your shaft to the gearbox and moving the shaft backwards or forwards by about 5mm. If the shaft is worn and that's the reason for the leak then this will place a new area of shaft on the seal and might cure the leak. I know someone who did this and 5 years later it's still fine. Ultimately you probably need new seals but it's got to be worth trying a workaround.

Edited by blackrose
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Silly question time. Is the dripping water definitely coming from where the prop shaft goes in to the stern gland? Is it worth checking the water hoses and plumbing too and from the gland? In particular, that type of braided clear hose has a tendency to harden and leak around joints and hose clips in quite a short time span.

Jen

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5 hours ago, Old Son said:

You will probably find a new gland is required. If the existing gland has worn a little part of your prop shaft down you might also find a new Vetus unit will leak. I fitted a shorter unit to a friends boat so the new gland ran on a new section of prop shaft. I think it was a Radice gland. Plenty of information on this site from Catweasel and also on Google.

Wasn't it possible just to move the shaft a bit for the same result rather than replacing the entire gland? It only needs to be moved by a few mm to find a new unworn bit of shaft.

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4 hours ago, Nick D said:

Really? The engine has only done 400 hours!

It would be an early failure, but perhaps the previous owner neglected it or used the wrong grease.  Unlikely it will develop rapidly into anything sinister. I'd be inclined to read the greasing instructions and re grease it to get back to a known state of maintenance.  I have the simpler Volvo type which just needs an occasional finger full of silicone grease pressing into the interface between the rubber and the shaft where the sealing lip is. I don't know the exact arrangement of your Vetus job, but it might help to try that to make sure the lip isn't dry.

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Thanks all for the comments so far.  I will check alignment as far as possible by sight, the hoses to and from the unit look fine and the shaft turns fairly easily by hand (should it?). I didn't realise there was more than one type of silicone grease. This is what I have been using which looks similar to the one suggested by Cuthound.

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31 minutes ago, Nick D said:

Thanks all for the comments so far.  I will check alignment as far as possible by sight, the hoses to and from the unit look fine and the shaft turns fairly easily by hand (should it?). I didn't realise there was more than one type of silicone grease. This is what I have been using which looks similar to the one suggested by Cuthound.

 

Yes it should. As long as that grease is nice and thick it should be fine. How badly is it dripping anyway? Most conventional glands drip a bit while in use. As long as your bilge pump can handle it and it's not dripping when the shaft's not rotating it might not be such a big issue?

Another thing to try is taking the hose off the top of the gland to make sure water is coming through. If it's coming through with the engine off then it will be coming through with the engine on and in gear so no need to test that. If it's not coming through with the engine off then try it on and in gear to see if that forces water through. Just take care when stepping around rotating shafts, etc. 

Edited by blackrose
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The water dripping in is not deep enough for the bilge pump to cut in. I removed about 2 litres of water earlier after about three hours cruising and it doesn't leak when the gear is not engaged so I hope that it will get me home.  It's never been a problem until the last few days which is why I am concerned now.  I will try the hose thing tomorrow thanks.

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The double lip seal will need replacing.(common fault on these) .  From vetus this is about £90 ( they don't sell the seals separately but with the brass housing .....I haven't found a supplier for the seals alone). Easy to do  in the water but less stressful on the bank side.

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These seals should last thousands of hours without dripping (mine has done well over 2,000 hours with not a drop leaking).  If it is dripping it is usually down to misalignment of the prop shaft.  It will also start dripping if it has never been filled with silicone grease (I have seen this) or not topped up at the recommended 100 hours.  If it has been run for some time dry then it will probably have worn a slight groove in the prop shaft.  You can usually move the prop shaft in or out about a cm to get on to a good bit.   If the boat is out of the water with the propshaft removed, if you look down the bearing you may see it looking shiny on one side - clear indication of misaligned propshaft.

These shaft seals are ideally used with a fixed thrust bearing or plummer block so that engine movement doesn't stress the seals.

  • Greenie 1
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9 hours ago, Richard10002 said:

Is it a drip less gland?

 

8 hours ago, Boater Sam said:

Supposed to be. I think I prefer a length of graphited gland packing and a spanner.

The very much simpler and cheaper (60 odd quid} Volvo one is totally watertight and requires very little attention. It just needs "burping", a simple squeeze til a little water is seen to release any air on fitting or going back in the water and then a tiny bit of grease every 200 hours or annually. I'm sure there's a reason why every Narrowboat builder doesn't use this set up, but I'm grateful mine did!

 

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11 hours ago, blackrose said:

Wasn't it possible just to move the shaft a bit for the same result rather than replacing the entire gland? It only needs to be moved by a few mm to find a new unworn bit of shaft.

The boat was in for blacking and we had a lot of painting to do. I didn't want to see how much spare shaft there was, find out there was not enough and then have to find a stockist for the new parts. As it was the shaft was seized in the gearbox end, we could never have done this change over in the water. Maybe it would have worked but the Radice Gland was actually cheaper than a replacement Vetus would have been.

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