Dripless Propshaft Seal - NOT!

[Professor Longhair]

Hello Folks,

Some info from the collective would be appreciated. I have a 2003 Beneteau 393 (US Build) in a Marina in Bundaberg, Queensland, Australia. You may have heard about the record flooding here in the last week or so. While many boats have been swept away, sunk or thrown on the rocks I have been very lucky and have sustained no harm. Well that was up until Saturday when I was doing a bilge check and general clean up. I found dirty, muddy water in the bilge.

Initially I thought any water might be from the defrosting of the fridge freezer which occurred when the power went out and the fridge kept running till the batteries were run flat ( there wasn't much sun about for a few days to keep the batteries topped up). But when I saw the colour of the water and how it matched the brown muddy slop that my normally clear blue/green marina had become I knew at once it was water from outside leaking in.

After a check of all through-hulls, I checked the Volvo Penta dripless propshaft seal, yes it was leaking.....

I work away from the boat on a 4/1 roster and only get to be on board one week out of five, when I do get on board I always do a quick but thorough check for water ingress and other potential dramas. I found no such drama on my initial check only the day before.

Now the flooding here has resulted in currents exceeding 35kts and that was maintained for a few days. I'm trying to work out how my supposed dripless shaft seal suddenly decided to start dripping quite badly and have come up with the following theory:

Boat points into the current, prop spins with current as gearbox is in neutral. Water line to cool/lubricate the Volvo Penta seal was turned off due to it being a through hull fitting which all get turned off when I leave the boat. Prop spins many times faster than normally required to propel boat at 7kts, no water to cool/lubricate seal and it heats up and fails.

Has anyone had a similar problem before? Should I now leave boat with prop seal cooling/lube line open or perhaps leave the gearbox in forward (or reverse) to prevent further excess revolutions?

Any advice, knowledge would be much appreciated.

Cheers

 

[Mrnotming]

Seems a good analysis Prof Longhair, glad you still have a boat!
Others will be along to help before long with this query.
I would engage a gear but for the worry if its a diesel it might run. But then again you may have a fuel stop on the engine?
What is the engine make and model?

 

[NormanS]

35 knots?

 

[martinaskey]

Likewise, glad the boat survived.
Suggest contamination might be the problem.
Maybe silt brought up by the floods has worked back to the seal .......
Just a thought.

 

[Talulah]

Silt in the sea water acts an abrasive. With the prop free to turn it has slowly abraded away.
I've seen this happen with the water cooling pump impeller when going upstream battling against a downstream tide full of suspended sand.

 

[30boat]

Those seals are tried and proven but the conditions were exceptional.With a fixed prop it might be a good idea to leave the box in gear or to fit a shaft brake.I don't believe you can start a diesel by drag on the prop alone.

 

[NormanS]

Those seals are tried and proven but the conditions were exceptional.With a fixed prop it might be a good idea to leave the box in gear or to fit a shaft brake.I don't believe you can start a diesel by drag on the prop alone.

You certainly can in some circumstances. I have started a Gardner 6L3 114hp, by getting the boat sailing, then putting the engine in gear, decompressing to get the engine turning, and then shutting the decompressors. Boat speed probably no more than 3 knots.

 

[philip_stevens]

I have not heard of or seen a VP shaft seal with separate water lubrication. I believe there is a similar seal with water lubrication.

Not sure what could have caused the seal wear though, except, as you say, lack of water lubrication, or has already been suggested, suspended grit in the water.

 

[Tranona]

You certainly can in some circumstances. I have started a Gardner 6L3 114hp, by getting the boat sailing, then putting the engine in gear, decompressing to get the engine turning, and then shutting the decompressors. Boat speed probably no more than 3 knots.

But that won't happen with the OPs engine, probably a Volvo as no decompressors and it needs glow plugs, so power.

 

[Professor Longhair]

Thanks paulclan,

I have a 45hp Westerbeke diesel in the boat. I'm no expert but I'm not sure that the water through the prop could generate the torque required to turn the engine over. But a fail safe would be to pull the engine stop cable.

Cheers

 

[sailorman]

with the ignition key off the fuel solenoid will be closed.No power = No fuel

Thanks paulclan,

I have a 45hp Westerbeke diesel in the boat. I'm no expert but I'm not sure that the water through the prop could generate the torque required to turn the engine over. But a fail safe would be to pull the engine stop cable.

Cheers

 

[Professor Longhair]

35 knots?

Norman,

Mate, reported speeds of up to 40kts but I wasn't there at that time due to being stranded by flooding elsewhere.

Cheers

 

[wotayottie]

Your analysis sounds possible rather than plausible. You are thinking that your seal has run dry, worn out and then suddenly become wet enough for water to get back in. {Possible . More likely is that some heavy material has been carried downstream by these flood tides, hit your prop and damaged the bonding of the stern tube to the hull. We have never had 35 kn floods but we certainly have had that sort of damage with rubbish being carried down stream by the current

Doesnt sound like a Volvo seal either because they do not have water flows into them and in any case they are grease lubricated

In your position it would be a lift out and a very careful; check for hull damage

 

[NormanS]

I just can't imagine how the boat would behave going through the water at that speed. I'm really surprised that your only problem was the shaft seal!
I'd have loved to watch it, (from a safe place).

 

[seumask]

I belive as a temporary fix you may be able to put a large jubilee clip or zip tie around it, stop the prop rotating and gently tighten until the drip stops.

 

[Professor Longhair]

Your analysis sounds possible rather than plausible. You are thinking that your seal has run dry, worn out and then suddenly become wet enough for water to get back in. {Possible . More likely is that some heavy material has been carried downstream by these flood tides, hit your prop and damaged the bonding of the stern tube to the hull. We have never had 35 kn floods but we certainly have had that sort of damage with rubbish being carried down stream by the current

Doesnt sound like a Volvo seal either because they do not have water flows into them and in any case they are grease lubricated

In your position it would be a lift out and a very careful; check for hull damage

watayottie,

It's definately a Volvo Penta seal, it's described in detail in the manual and I have googled it as well. Apparently there is two seals on it one lubricated by water and the other by grease on assembly. There is a water inlet from a screend through hull fitting which appears to be at such an angle that it catches the slipstream water and sends it, via a hose into the stern tube. Thats about where my understanding peters out.

The prop end of the boat was facing away from the water flow and while your suggestion is certainly plausible, hopefully its not what happened. The boat is going to come out of the water in any case, a careful inspection of all the surrounding area will also be done. Another problem is that there are so many boats needing lift out and repair that lift time and hardstand space will become very scarce.

I've bodgied up a fix to stop the water leaking in and have gained plenty of time to do the work, I guess the major reason for my original question is would that be a reasonable insurance claim?

Cheers

 

[Professor Longhair]

I just can't imagine how the boat would behave going through the water at that speed. I'm really surprised that your only problem was the shaft seal!
I'd have loved to watch it, (from a safe place).

Norman,

Apparently it was a sight to behold, there has been quite a bit of damage done to the berth fingers and quite a number of the concrete pontoons have broken away. One such piece with two yachts attached continued on to crash into a number of yachts further down the marina, sinking one. Due to being prevented from getting there by flood water I could only get there once the absolute worst was over. However I saw very high rates of flow down the river, so much so that the leading edge of the pontoons on my finger had been pushed down and were twisting the pontoons almost vertical. Even at these flows my boat was throwing its head about and thrashing from side to side.

A friend of mine went to the marina to check my boat for me and wouldn't venture out on the pontoon, the noise of the water rushing and the clanging about of the boats was quite violent and not safe for any reason.

Cheers

 

[reeac]

It sounds like a Volvo seal but "into the stern tube" makes me wonder whether the water feed is to supply a cutless bearing further along the prop. shaft.

 

[Professor Longhair]

I belive as a temporary fix you may be able to put a large jubilee clip or zip tie around it, stop the prop rotating and gently tighten until the drip stops.

seumask,

Great minds think alike, this is what I have done to stop water leaking in till I can get it lifted out. I have put the gearbox in fwd and as always , locked the steering in the central position.

Cheers

 

[Professor Longhair]

It sounds like a Volvo seal but "into the stern tube" makes me wonder whether the water feed is to supply a cutless bearing further along the prop. shaft.

Sounds feasible too reeac, the sum of my experience has been reading about the setup, I haven't any practical knowledge in this area even though I'm a trade qualified Diesel Fitter.