stuffing box blues

[fedor]

hi all,

I have a fairly old stuffing box on my boat, that is really a headache. it was OK when we bought the boat, but during the years it started to leak more and more. usually, tightening the nut and few squirts of grease helped, but some months ago it we've run out of tread to tighten the nut. we repacked the box the best we could and it was OK for some time. but, after about 60 engine hours of motorsailing she started to leak again. now, when we motor, salt water is sprayed from the box all over the engine compartment. it always leaks when motoring and we can to stop the leak when engine is not running only by huge dozes of grease pumped in. I can repack again, but it seems that it will not help.
at this stage I know about all the possible reasons for this problem - excessive engine vibration, worn cutless bearing, engine misalignment. could you please help me to identify the solution to my case?

a) vibration. not too much of it, although I do not have anything to compare to. engine (volvo 2002) seats on rubber mounts which are 5 years old. how do you know that the engine moiunts need replacing?
b)worn cutless bearing. there was a little bit of flex in the shaft when we hauled her out a month ago... how much of it is allowed, generally?
c)engine misalignment. I have 4 small rubber legs between two disks of prop shaft coupling, and my books do not say anything about checking flexible couplings for misalignment. how do you do it on flexible coupling? there is about 30 mm between disks - too big for feller gauge!

thanks in advance for youre answers.

PS another problem we have with our faithful volvo 2002 - it appears to be leaking oil down into the bilge. how do you find a place where the oil leaks out and what remedy do you suggest? (it is somewhere in the lower part of the engine - no oil drops on the visible part.)


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[jerryat]

Hi Fedor!

It sounds like the shaft itself is heavily worn to me, particularly if the boat is 'mature' and it's never been changed. Depending on the shaft diameter, and IF this is the cause, you can have it re-metalled for a reasonable cost which may prove more economical than a new one. You will need to dry out and check the shaft wear to ascertain if this is the reason, but aside from the gland itself leaking at it's junction with the stern tube, I can't think of another cause.

Hope this helps

Good sailing!

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[fedor]

hi!

can it be the wear of the cutless bearing or engine misalignment? we had to replace rubber legs last year (they sheared when we got a rope entangled around the prop)

is it possible to check for the shaft wear without taking her out of the water?



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[brianhumber]

If you have really been tightening the packing down hard over past years then it may well have scored the shaft. If this is case I am afraid its shaft out and remetal or new shaft.

Used to have this problem at sea when numbnuts overtightened the follower nuts becuase they thought the seal should be completely dry. Properly adjusted they last for years however.

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[jerryat]

Hi Fedor!

It may be that the cutless bearing is worn, but the fact that the ingress of water stopped, or was significantly reduced, after the fitting of new packing, still points to the gland itself or, more likely, a worn shaft. I do not believe it likely that the problem is with engine alignment or movement, unless one or both are blatantly excessive. From your description of events, neither of these seems the likely cause.

As I said earlier, I would try to dry the boat out alongside a quay or posts, remove the gland (here I am assuming that the stuffing box is attached to the stern tube via a flexible reinforced tubing or similar and relatively easy to remove) and use a micrometer to check the shaft diameter at the point of contact with the packing. Replace it as soon as you have taken two or three measurements along this area of the shaft. You should have plenty of time for this operation between tides. Take similar micrometer measurements on a clear, unworn section of shaft and compare the two.

I suspect that you may find a surprising difference that may result in your needing to either re-metal or replace the shaft. It's a pity the problem has manifested itself at the beginning of the season and don't know whether you could leave it until laying up time, when you can take more time over making a decision.

I'm sorry it all sounds so depressing, but I can't think of any other cause from your description and without seeing the situation.

I hope this helps you decide the best course of action and that it is successfully, and cheaply(!) sorted out.

Good sailing!

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[capsco]

If your shaft is worn , undo the coupling, slide the shaft back 1" and rotate it, if it clears the rudder, then have a 1" spacer made up to go between the two halves of the coupling, [you will need longer bolts] this will allow the packing to run on an unworn part of the shaft,

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[Robin]

You will still need to dry out but another alternative would be to fit one of the modern face seals such as the PSS Seal (don't go for the Deep Sea Seal). See

http://www.lakesterngear.co.uk/

They are in Poole and supply PSS seals

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[john_morris_uk]

PSS seals are the biz. Have used them more than once and not only are they reasonably priced, but they don't leak at all!

I have no connection with them except as a satisfied customer.

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[Robin]

John

That's good to hear since we just fitted one to replace a Deep Sea Seal! So far it seems OK and much better engineered.

Robin

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[jerryat]

Hi Robin!

Yes, the PSS seal is a good idea and reputedly a good solution for a worn shaft, though I don't like the things personally. I don't know the relative cost between a PSS and re-metaling, but suspect there isn't much in it, so it gives a good alternative. However, is it relatively certain that a PSS could be fitted 'twixt tides without previous experience and everything going perfectly?
Unfortunately, our friend would have to have his boat lifted for the re-metaling/new shaft solution which is why I hope he can struggle on until the end of the season and look at all possibilities without any pressure.

Out of interest, have you had problems with a Deep Seal installation?

Good sailing!



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[Robin]

Fitting the PSS is very quick - once the shaft is removed from the coupling which could be a nuisance if corroded, but this could be done afloat.. You would also need to have space between the rudder and prop to slide back the shaft slightly to fit the seal.

The PSS seal has a rigid S/S face mounted to which the graphite seal mates, the seal area is wider than on the DSS and accepts more engine movement I believe. We had an occasional problem with our DSS with engine movement in really rough seas (soft mounts) resulting in an occasional water ingress - occasional isn't good enough in my book. Others have had more serious problems (a search will bring them up). The PSS is a more robust piece of engineering IMHO as others too have reported.

Robin

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[jerryat]

Hi Robin!

Many thanks for that. I knew the principles re the PSS and similar but was interested the downsides. Hadn't realised they, at least the Deep Seal, wouldn't cope with significant engine movement. Still don't fancy them and use the Volvo 'lip seal' type. Minimal maintenance, cheap, totally watertight and have just changed mine after exactly 20 years. And this was only because I'm doing a major refit including changing the cutless bearing, also 20 years old.

Glad you're pleased with the PSS though and it's good to know of good quality, effective alternatives. I suspect Fedor will go down this route if the water ingress is too unacceptable to leave until the end of the season AND he could change over between tides. You mention of a corroded, jammed shaft etc is the sort of problem though, that might make a returning tide 'interesting'!!

Thanks again.

Jerry

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[Robin]

Hi Jerry

The Volvo seal has had good press on here, but is not available in a size to fit our shaft and sterntube combination so wasn't an option. As far as Fedor's problem is concerned I'm not sure a rotating lip seal is a good idea on a possibly worn shaft? If he wanted to fit a PSS or similar then it might be sensible to disconnect and then replace the shaft & coupling beforehand (it can be done whilst afloat), just to make sure it could be done in anger when time is limited by the tide return.

Back to face type seals in general, the PSS certainly will accept more movement and or misalignment than the DSS but either should be OK. The DSS though has a flexible (rubber mounted) face on both parts and it is difficult to install the shaft mounted part exactly at 90 degs to the shaft, even with the template they supply. The PSS has a rigid S/S collar fitted to the shaft which gives IMHO a much more consistant surface for the other half of the seal to rotate agains, plus the corrugated hose of the PSS is more robust at applying pressure on the seal face. In our case we had an occasional leak with the DSS under sail in very rough conditions, but occasional is too often in my book and so far at least the PSS has been OK.

Robin

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[dickh]

Hi Robin,
My shaft sounds similar to yours, the Volvo seal is not available in our shaft/stern tube combination and I don't have enough room to fit the PSS seal, which I consider to be better engineered. So I will probably bite the bullet and fit a DSS seal if my leakage gets too great. So far I'm OK with occasional gland tightening and regular greasing.

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[Robin]

Dick

There is nothing wrong either with the old style packed and greased gland, just in our boat (which came with a DSS) the area under the shaft, and the area under the engine (separate but adjacent of course) are sealed, so that any water there doesn't find it's way to the normal bilge sump. I believe this is done for 'environmental' reasons to avoid oily water being pumped overboard. Our boat is very dry and in fact normally completely so, therefore when the seal does leak and it collects in a flat area it is a pain to sponge out, needing removal of bedding, cushions etc in a stern cabin and the usual contortions torch in teeth and sponge in hand. We have an auto pump in place (came with the boat) but this is about useless, the areas are very flat and the pump sucks air mostly. These seals are supposedly completely watertight, well in our case the DSS wasn't but (so far) the PSS is. That said our old boat had a packed/greased gland that never leaked water though it did sometimes spray a film of grease about!

Robin

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[fedor]

hi all

thanks for your answers - it was very informative, although i am still not convinced that the reason for our troubles is wear in shaft. i will try to do the micrometer test when I have a chance - boat is currentlly in Marmara sea en route towards eastern Black Sea, and it is quite difficult to dry out here
PSS looks like one possible solution, I must read more about it.
I like the idea of shifting the shaft for an inch or two by adding some spacers. This is a quick fix and it can be done in the water by adding some thick washers on top of existing rubber feet between coupling disks. Cheap, too. I will try that as soon as I get to some decent hardware store.

still, one question remains. how do I check for engine alignment on flexible coupling? (one with rubber feet)

again, many thanks for all your answers


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[roger]

Another suitable seal of the PSS type is the Stopelo which is French.
I bought a 25 mm. seal in the chandlers opposite Yacht Club Mer du Nord at Dunkirk for about 90 pounds. Its worked perfectly.
Note - do remember you need to flood the seal everytime the boat goes into the water or it catches fire when run dry.

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[connacht]

I fitted a DSS to replace a stuffing box at the start of the season. Was surprised to find that it included a small inlet pipe which is supposed to be connected to a water supply - the exhaust water was suggested. I have not done so and am running the seal with a plug in the water inlet pipe. Any advice on the necessity or otherwise of a water supply and any suggestions on an easy way to connect it?

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[tome]

There are 2 types of PSS seal - standard and high speed. The high speed one is for boats with hull speeds more than 12 knots. Our 37 ft sailboat is fitted with the dry standard type and it works very well.

On your boat it should not be necessary to feed water to the seal and it sounds like you were supplied the incorrect model. Plugging it sounds like the best option.

Read more <A target="_blank" HREF=http://www.shaftseal.com/the-two-types-of-pss-shaft-seal.html> here </A>.

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[Richard_Blake]

Looks like the forum engineers are out sailing, so I'll have a go, as your system sounds like ours. The flexible coupling is mounted between a flange on the shaft exiting the gearbox, and a flange mounted on the end of the shaft, right? I'm afraid you have to remove the flexible coupling from between the flanges, slide the shaft forward until the two flanges just touch, and align these two with a feeler gauge if nothing more high-tech is available. Check that their centres are in line, and check round the edges with the gauge to see if the alignment is out, and where. Rotate the shaft a quarter turn, and repeat. And again, and again. Make a note of all measurements, adjust the engine feet as necessary, and repeat whole process. This will also tell you if your shaft has any unacceptable bend in it. If you are among cruising yachties, try and borrow a book such as Nigel Caulder's on boat mechanics and maintenance. Good pictures of the process. Incidentally, removing the flexible thingy and sliding the saft forward to do this will also expose the bit of the shaft from inside the stuffing box which may or may not be worn.

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