I replaced the prop shaft on my Santana last year and found it was blessed with a stuffing box that was completely stuffed so I invested in a dripless seal supplied by a South Australian company. It works brilliantly and I am very pleased with it, however, I've heard that when these things fail they fail 'catastrophically' so I need to know what to look for as an indicator that trouble is imminent. If you are on board when it happens there is a 'failsafe' device you can operate to stop the ingress of water, but if you're not, well........So what do I look for and how long are they supposed to last for?. I thought engine heat may be a problem but the seal is filled with water so it should stay cool. Anybody with experience with these devices?.

Why not put your concerns to the company that supplied the seal and ask what their recommendations are regarding care and maintenance and things to look out for.

I have also just replaced my dripping seal with a pss dripless one
there are precautions mentioned in the installation instructions
and on various web sites
a ss clamp is the simplest insurance in case the grub screws let go

Hi scaramouche. The seal that I received does not have grub screws, each half is held by a pair of ss clamps. my concern was more to do with the deterioration of the rubber component. Is there any outward sign of imminent failure or possible progressive signs that it will fail in the not too distant future. What will you look out for ??,
LC. I didn't see anything pertaining to component failure, only to ensuring that no lubricant was used during assembly.

Never had to touch it but gave me a few sleepless nights when l learned how it works.
I keep it clean, lubricated it with rubber grease, keep my eye on the calmps, make sure my powerful bilge pump is working, check my batteries too, insurance current, prayers done. Hope dies last.

Thanks sirgallivant. I've had no sleepless nights but maybe I'm too trusting. I hadn't given rubber grease a thought, I guess it would help to stop it drying out. Good pic of yours thanks, my bellows seem to be somewhat larger but its clamped on the same. Do you find that only the slightest bit of effort is needed to pull them apart for the water to spurt in, a bit scary. However no trouble to date, so.................

Not sure if this is truth or myth but a local chandler here told me to be careful if I ever pick up a rope around my prop shaft

He said what can happen is the rope wraps around the shaft like a Spanish windless and can force the prop and shaft backwards and force the shaft mounted forward half of the dripless seal forward on the shaft ( I guess it can flex the engine rearward on the flexible mounts)

When the rope is removed and the shaft moves forward again there is to much clearance between the front and rear sections of the dripless seal and the boat can take on water without the owner realising what has happened

Regards Don

Oh yeah, the slightest sideways push on the rubber could make it squirt quite substantial amount of sea water into your boat. That is, why there is nothing around it to touch it. The well must be clean and empty of all materials. It is a most vital part. Everybody is worried about the sea cocks but they are bomb-proof compared with the drip seal.

Though l never heard what Donk mentioned, l find it quite possible. Ropes or God forbid chain around the prop shaft very well could ruin anybody's day.
I rather not experiment with it.

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Donk107 said..
Not sure if this is truth or myth but a local chandler here told me to be careful if I ever pick up a rope around my prop shaft

He said what can happen is the rope wraps around the shaft like a Spanish windless and can force the prop and shaft backwards and force the shaft mounted forward half of the dripless seal forward on the shaft ( I guess it can flex the engine rearward on the flexible mounts)

When the rope is removed and the shaft moves forward again there is to much clearance between the front and rear sections of the dripless seal and the boat can take on water without the owner realising what has happened

Regards Don

Whats on your sail master Donk Ive the old rope and give it a grease when your done for the day

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HG02 said..

Donk107 said..
Not sure if this is truth or myth but a local chandler here told me to be careful if I ever pick up a rope around my prop shaft

He said what can happen is the rope wraps around the shaft like a Spanish windless and can force the prop and shaft backwards and force the shaft mounted forward half of the dripless seal forward on the shaft ( I guess it can flex the engine rearward on the flexible mounts)

When the rope is removed and the shaft moves forward again there is to much clearance between the front and rear sections of the dripless seal and the boat can take on water without the owner realising what has happened

Regards Don

Whats on your sail master Donk Ive the old rope and give it a grease when your done for the day

Hi HG

I have a dripless type (brand and age unknown) that seems to be ok for the moment

It looks a bit like this photo I found on the net and seems to have two faces (possibly ceramic or carbon like a truck water pump seal) that bear up against each other





Regards Don

Don.
That dripless seal pictured is exactly the one I've got. It's a Manecraft EM seal. My original question concerned deteriation of the rubber bellows and whether it would be visible well before it failed........or am I just worried about nothing.

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samsturdy said..
Don.
That dripless seal pictured is exactly the one I've got. It's a Manecraft EM seal. My original question concerned deteriation of the rubber bellows and whether it would be visible well before it failed........or am I just worried about nothing.

Yes.

Is your vessel a Santana 30?

The seal is out of the sun and there will be very little heat. Mine a Volvo dripless seal I think. I glance at it every six months or so. Supposed to burp them when you come off the slips but I always forget.

Hi Ramona. My boat is a Santana 28. Me and the Missus have been renovating her for the last twelve months and upgrading a few things (the dripless seal was one) and we are now teaching ourselves to sail.

Don.
From memory each half of the seal has a face of different material, I think one being carbon.

Ramona.
The seal has two plastic hoses (small dia) that allow the water to fill the seal without trapping air. These of course have to be tied up well above waterline, I guess that negates having to 'burp' it.

Since selling our NS33 yacht last year, I have been busy finishing off another boat, hopefully for launch in March.

Have tried to change over my Seabreeze user name from Cool Runnings, but not so easy to do .That name went with the yacht down to Jervis Bay. Anyway, you lot will have to put up with me under the same guise again.

Sam, I have just fitted last week a PSS shaft seal onto a inch and one eighth shaft.

In the main, they are reliable, but I would be replacing parts like hose clamps and nitrile rubber bellows between the 5/10 year period.
That would depend on condition as it presents itself, but also keep an eye on the metal collar and carbon collar faces.

Hey Cool Running, is that my imagination, lighting effect or camera angle that makes the shaft appear to be not lined up with the centre of the stern tube? Or is it just how the bellows has bunched up. Just how tolerant are these seals to misalignment or shaft vibration.

I've been thinking about putting one on my boat. I see the PSS range are water cooled but the picture of Sirgalli's isn't. How did you connect in your cooling water. I'm always a bit concerned about diverting any of my raw water away from the engine cooling system. I was tempted to put in a separate pump.

I also have a steel boat but my engine is bolted down hard. I was always under the impression that with an engine that has flexible mounts, you need a flexible coupling for the drive shaft (plus maybe a shaft support). And if the engine is solid mounted then no flexible drive shaft coupling is required. And my Yanmar installation manual (be it very old) agrees with me. The alignment and support of my drive shaft is directly related to the position of my motor. (could be wrong again )

Cheers Crusoe

Hi Crusoe-We did fine tune that aligment aspect you so dutifully picked up on.

In answer to your question,the water delivered to the PSS is tee'd off the waste side of the cooling circuit onto the barb you see on the carbon block.This waste water ends up in the exhaust or in our case with the dry stack ,directly outboard anyway.
Therefore there is no loss to the engine cooling in that aspect.It is important that there is not too much water going into the shaft seal and we are attaching a 6mm hose only.
.
Most seem to go with flexible mounts and couplings these days to minimise vibration and allow ease of set-up .Also in the event of a tangled prop ,this would be more forgiving on the drivetrain than say a rigid set-up.(Broken engine mounts,snapped keyways etc)

We set the shaft in position in the first instance without the flex coupling to within a few thou of the engine.The shaft was slid back and then hooked up the Polyflex coupling again.The bellows was preloaded 20mm aft and the S/S hub tightened up to finish.Having flexible mounts and couplings probably does not mean that you can be rough on the lignment etc.

I will be running the engine on the hard for a while before launching to 'bed' in the fittings of the shaft,as the manufacturer mentions there will be some leaks or misting until it takes up.

Check out www.coxengineering....
It explains everything.

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CoolRunnings said..
Hi Crusoe-We did fine tune that aligment aspect you so dutifully picked up on.

In answer to your question,the water delivered to the PSS is tee'd off the waste side of the cooling circuit onto the barb you see on the carbon block.This waste water ends up in the exhaust or in our case with the dry stack ,directly outboard anyway.
Therefore there is no loss to the engine cooling in that aspect.It is important that there is not too much water going into the shaft seal and we are attaching a 6mm hose only.
.
Most seem to go with flexible mounts and couplings these days to minimise vibration and allow ease of set-up .Also in the event of a tangled prop ,this would be more forgiving on the drivetrain than say a rigid set-up.(Broken engine mounts,snapped keyways etc)

We set the shaft in position in the first instance without the flex coupling to within a few thou of the engine.The shaft was slid back and then hooked up the Polyflex coupling again.The bellows was preloaded 20mm aft and the S/S hub tightened up to finish.Having flexible mounts and couplings probably does not mean that you can be rough on the lignment etc.

I will be running the engine on the hard for a while before launching to 'bed' in the fittings of the shaft,as the manufacturer mentions there will be some leaks or misting until it takes up.

Hello Coolrunning thanks for the reply. I like how you plan to connect the cooling water in for the seal. Having my engine solid mounted does cause vibration and it would be probably worth my effort to fit flexible engine mounts and coupling as you have done. Hope all goes well with the install. Cheers

Thanks CoolRunnings. One tip I was given was to treat the seal as a "consumable" and change it every ten years regardless of how good it looks. Not a bad Idea.

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sirgallivant said..
Check out www.coxengineering....
It explains everything.

Thanks for the link on the seal Sirgallivant. I see that they are just an older model PSS Seal which has to be manually burped if air is trapped in the seal area after slipping the boat. I was under the impression that the tube on the newer PSS seals was for water injection/cooling but it seems the cooling/injection requirement is only required on boats travelling >12knts. Learning all the time

Hers a question for the experts.

If I have a dripless seal with no injected water cooling, will the stagnant water strapped in the stern tube end up de-oxygenated, resulting in possible crevice-corrosion in the S/Steel stern tube or S/Steel drive shaft

Cheers

All good!
Also the VETUS-MAXWELL site is worth investigating.

With the stagnant water, l guess the current is moving some water in and out. I know we are all sitting in a Mulligan's stew, in the major centres in Oz but the pond is not that stagnant. Realy.

Wouldn't the forward motion tend to "suck" the water out.??

wheres a good source for the PSS seal kits you guys any cheaper than others?

Here is the stainless part of PSS, it is quite deeply pitted possibly from sitting. It may have been sacrificing itself to the
more noble carbon/graphite seal face ( this would also explain why it has a nylon hose barb for the bleed) and maybe just a bit of crevice corrosion too. The other counterpart of the seal looks fine.

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Jolene said..
Here is the stainless part of PSS, it is quite deeply pitted possibly from sitting. It may have been sacrificing itself to the
more noble carbon/graphite seal face ( this would also explain why it has a nylon hose barb for the bleed) and maybe just a bit of crevice corrosion too. The other counterpart of the seal looks fine.

The PSS web site I found some PDFs there and in one it suggested if you motor trans has been sitting a while push the belows back and slide cloth in be tween the surfaces and move it around to clean the sealing area abd press it open to flush the grime out
How old is the seal Jolene ?

The PSS seal to me looks like a normal mechanical seal used in industrial plants and irrigation pumps basically.
I had a quick look at the Tides Marine seal . Quick meaning less than 60 second but it appear to use a neoprene type seal modified with different materials and retaining spring much like a timing seal in a car or truck with the extra parts so it fits marine use.
To me the PSS seal is a better design but its all choices and personal taste
I'm looking forward to a dry bilge when I fit one

Not sure how old it is HG02, I was asked by the owner of it if I could clean it up or make a new one. He was quite happy when I suggested he could simply reverse it and I could face the pitted side for him. I asked him if it was leaking and he said No. Quite an easy fix compared to making a new shaft or building up wear on a shaft from a gland packing.

Latest first hand info about to burp or not to burp a dripless seal?
My boat spent two days on the slip. When l got it back l did not burp the seal on purpose, l motored to the other side of the bay, about five minutes, and tied up.
I burped it after this and it had burped then water started flowing!
There was air inside, the water pressure did not push the air out as l thought it might!
So l suggest to burp your dripless seal after you had it out of it's element.

Im not looking forward to removing my transmission to prop coupling I don't think its been off since it was built in 1977 Appears to be aluminum .
What a good brand replacement

Right HG, my coupling was a pig to disengage the prop shaft for the same reason (not been off since the 70's) it was rusted and looked derelict, however, after taking the four bolts out and putting a wedge in the slot and giving it a few whacks with a lump hammer the shaft came out. I cleaned up the coupling with a wire brush to get a good look at it and low and behold there was really nothing wrong, so a lick of red paint and a promise to glance at it every now and then and it's all good. Mind you the coupling is a fairly solid lump of iron and I don't think I will ever have to replace it.

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samsturdy said..
Right HG, my coupling was a pig to disengage the prop shaft for the same reason (not been off since the 70's) it was rusted and looked derelict, however, after taking the four bolts out and putting a wedge in the slot and giving it a few whacks with a lump hammer the shaft came out. I cleaned up the coupling with a wire brush to get a good look at it and low and behold there was really nothing wrong, so a lick of red paint and a promise to glance at it every now and then and it's all good. Mind you the coupling is a fairly solid lump of iron and I don't think I will ever have to replace it.

Bit late now but never go near your shaft or coupling with a hammer. The shaft is really easy to bend. Use the holes with bolts and a socket behind the shaft and force the shaft out with even pressure.