Water supply to PSS seal.

[doug748]

Thanks to the reminder in the recent thread I will probably refurbish my PSS seal this winter.

I want to provide a water supply from my Beta 20hp engine this time, rather than rely on a simple vent.
Has anyone done this? - Is there a really easy way?
PSS say the max pressure should be around 10psi, I think.

 

[Tranona]

Thanks to the reminder in the recent thread I will probably refurbish my PSS seal this winter.

I want to provide a water supply from my Beta 20hp engine this time, rather than rely on a simple vent.
Has anyone done this? - Is there a really easy way?
PSS say the max pressure should be around 10psi, I think.

It is only needed on high speed applications, and more because there is a tendency for water to be drawn out of the stern tube at high speed. No such problem on your boat (or any low speed low power application).

 

[doug748]

Boats that have a stern tube exiting through deadwood, with a bearing, also need a positive supply to avoid problems. I see PSS have amended their advice to reflect this. Water is drawn out and the bearing prevents it getting back.

 

[Tranona]

So how did you manage before as almost certainly your previous seal was a water lubricated stuffing box? The vent will ensure that any air is vented. If you have a stern tube with a white metal bearing at the outer end then not sure a PSS is suitable as even adding a water flow will not allow the water to escape. If, however as is more likely it is a cutless bearing water will flow in and out.

However adding a water supply is covered in the instructions. Just needs a T in the raw water hose from the pump to the heat exchanger then a hose to the barb fitting on the seal. A small amount of water will then be diverted to feed the stern tube.

 

[doug748]

We all aware of the grand theory.

I am still keen to hear how folks, with practical knowledge of this particular set up, tackled it.

Rent a gobs full of opinion with no practical advice or experience we have in abundance.

 

[Boatface]

Thanks to the reminder in the recent thread I will probably refurbish my PSS seal this winter.

I want to provide a water supply from my Beta 20hp engine this time, rather than rely on a simple vent.
Has anyone done this? - Is there a really easy way?
PSS say the max pressure should be around 10psi, I think.

I think this may be a very sensible idea, in the light of my recent experiences with a simple vent tube.
For 4 years I had a water leak that occurred occasionally after running the engine. After years of frustration, we eventually found that our correctly installed vent pipe was spewing water all over the engine when we went into reverse. The reverse spinning propeller had been forcing a jet of water under the boat, up the stern tube, out through its breather pipe and all over the engine.
I'm now trying to fix this with a non-return valve but if that doesnt work I will provide a water supply by teeing off after the raw water pump. A positive supply will also prevent the vent from getting blocked. Good luck with it.

 

[Tranona]

We all aware of the grand theory.

I am still keen to hear how folks, with practical knowledge of this particular set up, tackled it.

Rent a gobs full of opinion with no practical advice or experience we have in abundance.

If you want to hear from somebody who has fitted one to the same boat as you then you need to give far more information. Otherwise you leave people trying to work out exactly what your problem is.

So, this "particular setup" is a mystery until you explain exactly what it is.

I have plenty of experience of stern tubes, seals etc on which to draw but it is only useful if there is something more specific to work from, otherwise all you will get is suggestions based on some assumptions.

Anyway, the instructions from the manufacturer are perfectly clear. If you want to provide a water feed (which their current instructions say is not necessary) then follow the instructions particularly the Note 2 which advises how to fit one . You can get a kit from the manufacturer to do this.

BTW there is no "grand theory", only common sense and following instructions.

 

[Tranona]

I think this may be a very sensible idea, in the light of my recent experiences with a simple vent tube.
For 4 years I had a water leak that occurred occasionally after running the engine. After years of frustration, we eventually found that our correctly installed vent pipe was spewing water all over the engine when we went into reverse. The reverse spinning propeller had been forcing a jet of water under the boat, up the stern tube, out through its breather pipe and all over the engine.
I'm now trying to fix this with a non-return valve but if that doesnt work I will provide a water supply by teeing off after the raw water pump. A positive supply will also prevent the vent from getting blocked. Good luck with it.

None of that will work because the OP claims his problem is that he has a bearing that will not allow water to flow back in. So his problem he claims to have is lack of water flow, not excess.

 

[doug748]

I think this may be a very sensible idea, in the light of my recent experiences with a simple vent tube.
For 4 years I had a water leak that occurred occasionally after running the engine. After years of frustration, we eventually found that our correctly installed vent pipe was spewing water all over the engine when we went into reverse. The reverse spinning propeller had been forcing a jet of water under the boat, up the stern tube, out through its breather pipe and all over the engine.
I'm now trying to fix this with a non-return valve but if that doesnt work I will provide a water supply by teeing off after the raw water pump. A positive supply will also prevent the vent from getting blocked. Good luck with it.

Thanks for that. Yes, your seal may have been running hot, in forward, due to insufficient water supply, this can lead to spray leaving the rotor. If you have a stern bearing note the new advice from PSS:

"15. Plumbing the system:
Note: Sailboats or displacement powerboats with a powering speed below 12 knots can use either method A or B.

....... However, displacement boats with a bearing in the shaft log.......... must plumb water to the seal"

Thanks again.

 

[BabaYaga]

Interesting thread... I also have a PSS seal on a 20 hp Beta, long keeler with cutless bearing in the stearn tube. My seal is 12 years old and an earlier model with no fitting for a vent tube/water feed. I am not aware of any problems with this set up, but perhaps I should worry about over heating?

 

[macd]

perhaps I should worry about over heating?

Only if it overheats, which is easy enough to check after a run. It's unlikely to be deprived of water with a cutless bearing. Or after having behaved itself for 12 years.

 

[BabaYaga]

Only if it overheats, which is easy enough to check after a run. It's unlikely to be deprived of water with a cutless bearing. Or after having behaved itself for 12 years.

Will certainly investigate. I suppose there will be some heat after along run, but should be touchable?

 

[Tranona]

Thanks for that. Yes, your seal may have been running hot, in forward, due to insufficient water supply, this can lead to spray leaving the rotor. If you have a stern bearing note the new advice from PSS:

"15. Plumbing the system:
Note: Sailboats or displacement powerboats with a powering speed below 12 knots can use either method A or B.

....... However, displacement boats with a bearing in the shaft log.......... must plumb water to the seal"

Thanks again.

That is potentially misleading. All stern tubes like the one you describe have bearings BUT not all bearings are the same. There are basically 3 types. Grease lubricated white metal, but rarely seen nowadays, composite water lubricated or fluted rubber such as the common cutless bearings. They behave differently with respect to water flowing into the stern tube. Composite run to closer tolerances and often require a positive water feed. For example, Beneteau which is probably the major user of composite bearings (together with water lubricated Volvo seals) fit a water feed using a skin fitting and scoop to ensure the seal is always wet. This is doubly important because their tube is fairly close to the waterline compared with a more traditional skeg.

The common cutless bearing usually allows plenty of water into the stern tube, particularly if there is a vent. That is what it is designed to do so it is rare for the seal to be starved of water. So, if as is likely you have a cutless bearing a positive water feed is probably not necessary unless of course you are experiencing overheating of the seal or excessive wear.

It would be helpful if the manufacturer gave more background to its changed recommendation given that there are probably many boats with "conventional" stern tubes that have been running for years without any problems.

The problem Boatface describes is very different from yours and I suspect that his boat has an open stern tube and a P bracket. What he describes is not uncommon in my experience - indeed in the early days of this type of seal it was not unknown for back flow of water in reverse or when surfing down a wave for the pressure of water to open up the faces of the seal and squirt water into the boat. The first thing for him to do is raise the level of the vent tube at least to the minimum recommended by the manufacturer. If water is flowing up the tube that well there is no need for a water feed, although of course would stop water coming up a vent tube.

BTW I would appreciate that when I am giving you sound advice based on the information you have given you refrain from being rude to me in response.

 

[doug748]

Will certainly investigate. I suppose there will be some heat after along run, but should be touchable?

It should not be more than a little warm.
I agree with macd, if you have experienced no problems (typically - squealing, seal flicking off centre, rime of salt building up around the seal) then probably all is well.

My thoughts are that problems depend on your prop design, hull and aperture size, type of bearing and clearance. Difficulties show themselves only after a long period of higher rpm running.

 

[doug748]

Apologies for bringing this back from the dead but I was contacting Beta on another matter and brought this up.

They suggested a dead simple way of sorting out a feed - tap into the flexi supply to the anti syphon valve, on the engine side. A tee fitting and a couple of jubilee clips and Bob's your uncle.

 

[rogerthebodger]

Apologies for bringing this back from the dead but I was contacting Beta on another matter and brought this up.

They suggested a dead simple way of sorting out a feed - tap into the flexi supply to the anti syphon valve, on the engine side. A tee fitting and a couple of jubilee clips and Bob's your uncle.

Won't that defeat the function of the anti syphon valve.

 

[doug748]

Dunno.

But I expect that the water should fall towards sea level on the supply side so that as long as the tee is comfortably above the static waterline all might be well.

 

[rogerthebodger]

Dunno.

But I expect that the water should fall towards sea level on the supply side so that as long as the tee is comfortably above the static waterline all might be well.

But air will not be able to enter the to break the syphon this will cause water to syphon back and enter the exhaust.

 

[BabaYaga]

But air will not be able to enter the to break the syphon this will cause water to syphon back and enter the exhaust.

In my view, as long as the tee is on the engine side of the anti syphon valve no harm will be done.
It would be different if the tee was between the anti syphon valve and the exhaust bend injection point.

 

[Hoolie]

Apologies for bringing this back from the dead but I was contacting Beta on another matter and brought this up.

They suggested a dead simple way of sorting out a feed - tap into the flexi supply to the anti syphon valve, on the engine side. A tee fitting and a couple of jubilee clips and Bob's your uncle.

That's exactly where it is on our boat and it works just fine. It certainly doesn't interfere with the anti-syphon valve in any way at all.