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Shaft seal drip, drip, dripping


OYSTR

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Can anyone tell me what type of shaft seal I've got here, other than a grubby and leaking one

2c53cbeb.jpg

 

http://www.youtube.com/watch?v=ZlJyrzFwoRQ

 

It used to leak a little only when motoring, now it's all the time. I've greased the stuffing box end so much that the grease is oozing out around the collar but made no difference. Assume it's a haul out and replace rather than adjustment job.

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To me it looks like more of a repacking job. Have you tried removing the rubber seal to see what it is packed with??

 

Somehow I think that it will be a teflon packing that will require removal of shaft. We did replace one in the water once. Wasn't to bad to do as we couls slide the shaft back far enough to get the new seal etc on it. Mind you my mate who was holding the rags around the shaft did get rather wet.

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No I haven't but I assume if I did it would flood the boat. The leak is coming out between the white plastic body and the black inner ring or the shaft itself. Given there is cooling water going into this plastic body from the engine water intake, when it's running, I expect I'm going to have to fix this bit rather than the packing in the hose.

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It's called a "Dripless" shaft seal. The part held in the rubber tube is fixed and the part on the shaft spins with the shaft. The two are pushed hard togethger and the water tube maintaines lubrication for cooling. There is no gland packing in these things. Also you do not grease it. You need to replace those two seals.

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It's called a "Dripless" shaft seal. The part held in the rubber tube is fixed and the part on the shaft spins with the shaft. The two are pushed hard togethger and the water tube maintaines lubrication for cooling. There is no gland packing in these things. Also you do not grease it. You need to replace those two seals.

Ok, thanks. I was greasing it through the grease nipple at bottom left.

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I've got a 'dripless' Volvo seal and the instructions are to grease it at least annually. OF course it came with some very expensive-looking Volvo grease, but it looks just the same as the blue marine grease you can buy in big pots from the swindlery.

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I strongly suspect that it is a one off manufactured seal that contains a standard lip seal or 2. I seen a few shaft seals in my time and haven't seen one that looks like that. Our boat has a similar setup and I changed it recently with the boat in the water by pulling the engine forward, removing the coupling and seal assembly and securing a bicycle inner tuber over the whole tube and shaft while I measured everything up and ordered bits from NZ. If it is that type of seal you will be able to source lip seals cheaply from any engineering supplier but replace the standard lip spring with an appropriately sized O ring to prevent rust. However many seals the unit contains, slide the same number of spare seals over the shaft between the seal assembly and coupling and next time it's a piece of piss to change.

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I strongly suspect that it is a one off manufactured seal that contains a standard lip seal or 2. I seen a few shaft seals in my time and haven't seen one that looks like that. Our boat has a similar setup and I changed it recently with the boat in the water by pulling the engine forward, removing the coupling and seal assembly and securing a bicycle inner tuber over the whole tube and shaft while I measured everything up and ordered bits from NZ. If it is that type of seal you will be able to source lip seals cheaply from any engineering supplier but replace the standard lip spring with an appropriately sized O ring to prevent rust. However many seals the unit contains, slide the same number of spare seals over the shaft between the seal assembly and coupling and next time it's a piece of piss to change.

 

 

Agree...I have seen a lot of seals but dont know that one.

 

It interests me the whole O ring thing...

To be blunt Idont like that system.

I would (and have myself) the carbon bush to stainless "washer" type. the only O ring is inside the shaft to stainless washer interface. Very unlikely to fail.

What is very important to me regarless is pw method of containment. That is serious cruising practicality that you should just tuck into your memories back closet...you just may need

it !

 

A major fail of a stern tube water interface (or a stuffing box : ) ) can sink a boat...having some kind of plan may get you back to port.

Perhaps not everybody will have a bike inner tube ( I do because I have a bike on board)..but there are a heap of other things that will help.

Better to run the idea now and think what you have on board before it happens.

...and just as a possibility...cling film (glad wrap) and cable ties may just stop your boat from sinking...heaps of others...

Sorry sideways as usual

I would change to a pss seal.

Aint perfect because I dont like rubber bellows, but the best I have found so far.

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Thanks for all the replies. Wasn't planning on a haul out until next summer (assuming we have one) and being at Bayswater with no haul out its not that convenient (toying with moving up to GH for that and family reasons).

 

A little seawater in the bilge isn't going to do a lot of harm, but could I be up for catastrophic failure with this?

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Oh I forgot to say. This can be fixed in the water. Pump some grease into the tube, you should actually be able to remove the seal and not have too much water enter the boat. The bilge pump should easily keep up with whatever comes in.

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The bilge pump should easily keep up with whatever comes in.

I'll let the wife know since she'll be on it :lol:

 

Is this on the basis you slide the engine forward as noted above?

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Yes. If boat was out of water, then you could slide the shaft back. The problem is that water is right behind the seal and under that clamped black hose. So you can not easily remove all that and slide the shaft back without water blasting in under some pressure. Unless you are happy to get soaked. It can be done, but not comfortably.

What I would consider is to lift the boat up on the floating dock and then you could go about the work. Or if you could allow the boat to dry on a grid somewhere and do it between tides.

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When you're replacing it, you need to consider which type will suit your existing gear.

Lip seals work on sealing against the propshaft.

Face seals ( bellows types) don't, they compress the two faces of the two components. So it seems to me that if you're using an old shaft with all its history, maybe some scratches or worse gained over its lifetime, that a lip seal type isn't the best way to go. A new installation is different because you know the shaft will be pristine, eh.

Another aspect of lip seals is that they invariably want an extra bearing, vesconite or similar, in the shaft log right beside the seal. So you have to be able to fit one of those.

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A good way to stop the boat sinking is jump over the side and jam a couple of turns of denso tape into the tube. Make sure there is an end free to get it out again. Usually gives 100% seal.

I agree with other's comments regarding lip seals, I much prefer face seals. Manebar (I think) make a PSS type seal with an emergency get home clamp if the seal disintegrates.

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Manecraft.John Crane seal. Yeah good seal but a casualty of corporate profit margins/ targets, they doubled the price ( literally) 18 months or so ago.

Auckland engineering have them ( or had them) .Whitings have PSS.

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