Any advice on engine water issue please?

[SiteSurfer]

I’m currently away and have found an issue with my sea water cooling system which only manifests itself after sailing.

here’s what happens, we motor for a while (everything working 100%) and then put up the sails,turn off the engine and then when starting the engine again the water fails to continue to circulate through and out of the exhaust.

I have to manually fill the strainer and prime it - upon which-it all works again perfectly.

this however never happens if we stop the engine after motoring and start it again. Only after sailing.

I hve recently changed the impeller and lip seal on the water pump just in case (the problem was there before) and am confident that this is air tight as no leaks.

given that the water appears to drain back down the pipe into the sail drive and not through the water pump I am suspecting it’s the Volvo (16 year old) strainer.

would that be a reasonable assumption? Or perhaps the anti siphon valve.

just can’t understand why sailing makes a difference!

 

[Beneteau381]

I’m currently away and have found an issue with my sea water cooling system which only manifests itself after sailing.

here’s what happens, we motor for a while (everything working 100%) and then put up the sails,turn off the engine and then when starting the engine again the water fails to continue to circulate through and out of the exhaust.

I have to manually fill the strainer and prime it - upon which-it all works again perfectly.

this however never happens if we stop the engine after motoring and start it again. Only after sailing.

I hve recently changed the impeller and lip seal on the water pump just in case (the problem was there before) and am confident that this is air tight as no leaks.

given that the water appears to drain back down the pipe into the sail drive and not through the water pump I am suspecting it’s the Volvo (16 year old) strainer.

would that be a reasonable assumption? Or perhaps the anti siphon valve.

just can’t understand why sailing makes a difference!

You perhaps have an air leak in to the system and the sailing causes a venturi effect which drags the water out of the system. The strainer O rings could be the culprit OR the anti syphon valve?

 

[Jamie Dundee]

I’m not familiar with saildrives but do you lock the prop (engine in gear) when sailing or leave it rotating?

 

[SiteSurfer]

I’m going to replace both in the morning, I hope Falmouth has them!
i think all the hoses and clips too just to be safe.

i leave in it neutral as it’s a fixed prop (as per Volvo instruction.)

 

[VicS]

You perhaps have an air leak in to the system and the sailing causes a venturi effect which drags the water out of the system. The strainer O rings could be the culprit OR the anti syphon valve?

The anti-siphon valve will let air into the system. It is designed to do that in order to break the siphon

 

[pvb]

... OR the anti syphon valve?

The anti-syphon should be after the pump, so shouldn't affect the priming.

 

[pvb]

given that the water appears to drain back down the pipe into the sail drive and not through the water pump I am suspecting it’s the Volvo (16 year old) strainer.

Grease the strainer O-ring with silicone grease.

 

[peter gibbs]

You perhaps have an air leak in to the system and the sailing causes a venturi effect which drags the water out of the system. The strainer O rings could be the culprit OR the anti syphon valve?

The Volvo trainer O ring becomes less reliable as it expands with time. A dollop of Vaseline works for me. But standing water in the system should not syphon out back down the S leg, as you describe, when the engine is resting. Replace the seal? But first check all connections are good - perhaps remake them? You know how it goes, you hit on an "obvious" solution that turns out not to be the case. That's sailing....

PWG

 

[SiteSurfer]

The anti-siphon valve will let air into the system. It is designed to do that in order to break the siphon

so is there any way in which a defective valve could be affecting this? It is after the water pump and I am confident that the water pump seal is ok. I suspect that the my initial suspicions and the confirmation above - it’s the strainer.

 

[Beneteau381]

so is there any way in which a defective valve could be affecting this? It is after the water pump and I am confident that the water pump seal is ok. I suspect that the my initial suspicions and the confirmation above - it’s the strainer.

A worst case scenario is that the water pump is worn on the sides allowing air to get in from the anti syphon valve and the water will "fall" back down the leg. Then the worn pump wont pick it back up. Thats for the pedants by the way! My money is on the strainer however.

 

[VicS]

so is there any way in which a defective valve could be affecting this? It is after the water pump and I am confident that the water pump seal is ok. I suspect that the my initial suspicions and the confirmation above - it’s the strainer.

No.
If the anti-siphon valve is working correctly it will open when the engine stops to allow air into the "loop" to break the siphon
If the anti-siphon loop is immediately after the pump water will drain until the level in the engine side is down to the level of the injection point into the exhaust and down to the outside water level in the pump side.

If the valve is stuck open water will leak from it when the engine is running.

If it is stuck shut air will not enter, the siphon will not be broken and you could flood the exhaust system and then the engine itself.

 

[Beneteau381]

No.
If the anti-siphon valve is working correctly it will open when the engine stops to allow air into the "loop" to break the siphon
If the anti-siphon loop is immediately after the pump water will drain until the level in the engine side is down to the level of the injection point into the exhaust and down to the outside water level in the pump side.

If the valve is stuck open water will leak from it when the engine is running.

If it is stuck shut air will not enter, the siphon will not be broken and you could flood the exhaust system and then the engine itself.

If the pump is worn on the pump faces it will allow the air allowed in by the antisyphon valve to leak past the pump and allow the water in the strainer to drain down to outside sea level. This is what happens on my MD22 when I loosen the strainer lid, the pump is on top of the engine. So to the OP, ignore us pedantic old bstds having a pissin contest and go and check the strainer seals and connections!

 

[Boater Sam]

If the pump is worn on the pump faces it will allow the air allowed in by the antisyphon valve to leak past the pump and allow the water in the strainer to drain down to outside sea level. This is what happens on my MD22 when I loosen the strainer lid, the pump is on top of the engine. So to the OP, ignore us pedantic old bstds having a pissin contest and go and check the strainer seals and connections!

And if the pump cover face IS worn, see if it will go on back to front.

 

[Beneteau381]

And if the pump cover face IS worn, see if it will go on back to front.

Si

 

[VicS]

If the pump is worn on the pump faces it will allow the air allowed in by the antisyphon valve to leak past the pump and allow the water in the strainer to drain down to outside sea level. This is what happens on my MD22 when I loosen the strainer lid, the pump is on top of the engine. So to the OP, ignore us pedantic old bstds having a pissin contest and go and check the strainer seals and connections!

If the water pump is higher than the outside water line then yes air entering via the anti siphon valve will allow the water to drain from the pump but that is a result of the position of the pump not due to any malfunction of the anti-siphon valve
Based on your earlier suggestion that the anti-siphon valve could be the culprit the OP was considering replacing it .... That would have been a waste of money because even a new correctly functioning valve would allow this to happen if the water pump is above the w/l.

The OP has not said what engine he has ... but from what he says about the age its unlikely to be an MD22

 

[SiteSurfer]

Hi folks, I’ve just replaced all the hoses and put a new Venus strainer in, thanks to Jerry at Falmouth Yacht Brokers (not related but awesome service).

we will see if this fixes the issue when sailing, it’s fixed a minor drip from the pump (which could have been the hose!) and seems to have if nothing else put us back to where we were. If this doesn’t cure the problem I will know tomorrow when we depart.

thanks so far!

 

[Beneteau381]

If the water pump is higher than the outside water line then yes air entering via the anti siphon valve will allow the water to drain from the pump but that is a result of the position of the pump not due to any malfunction of the anti-siphon valve
Based on your earlier suggestion that the anti-siphon valve could be the culprit the OP was considering replacing it .... That would have been a waste of money because even a new correctly functioning valve would allow this to happen if the water pump is above the w/l.

The OP has not said what engine he has ... but from what he says about the age its unlikely to be an MD22

3' 6"

 

[SiteSurfer]

Volvo MD2030 D if that helps.

 

[VicS]

Volvo MD2030 D if that helps.

It confirms that you should not have the same problems that afflict an MD 22

Where is your strainer mounted . towards the front of the engine or close to the sail drive

Hopefully your new strainer will have cured the problem but if not I was wondering if a check valve between the SD and the strainer would help or if it would introduce other complications.

 

[Beneteau381]

3' 6"

My first Beneteau was 1995, it had an MD2030, my 1999 Beneteau has an MD22, my Dutch mate has 2004 411 with an MD22 so age doesnt necessarily signify what engine. 4ft!