Any advice on engine water issue please?

[SiteSurfer]

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.

thats my next step. I will introduce a one way valve which I have lying around.

the strainer is very close to the the saildrive, slightly to the left so the pipe is not immediately vertical but has about 3/4 metre of length.

I am hopeful that this is an end to it. We are off to the Isles of Scilly in the morning so a good test as it looks like there may be at least “some” sailing involved.

 

[Old Harry]

thats my next step. I will introduce a one way valve which I have lying around.

the strainer is very close to the the saildrive, slightly to the left so the pipe is not immediately vertical but has about 3/4 metre of length.

I am hopeful that this is an end to it. We are off to the Isles of Scilly in the morning so a good test as it looks like there may be at least “some” sailing involved.

address the original issue not add in another problem

 

[SiteSurfer]

address the original issue not add in another problem

I have. It’s addressed.

In fairness I didn’t say I was going to fit the valve - just that it would be my next step (if this didn’t work).

 

[VicS]

I have. It’s addressed.

In fairness I didn’t say I was going to fit the valve - just that it would be my next step (if this didn’t work).

If you had a hull mounted water intake fitting I'd have suggested the problem might be air dragged under the hull while sailing, combined with pressure fluctuations as you ploughed through the waves finding its way up into the strainer but that seems unlikely from a saildrive immersed well below the hull.
The thing is though why does it only happen while you are sailing and not while peacefully moored or at anchor

 

[Jamie Dundee]

The thing is though why does it only happen while you are sailing and not while peacefully moored or at anchor

This is why I was wondering about whether the free spinning prop could be causing an issue.

 

[VicS]

This is why I was wondering about whether the free spinning prop could be causing an issue.

It's a thought but it's well behind the water intakes

 

[pawl]

hi, I had exactly this problem when I first had my present boat, not a sail drive though. I tried everything to cure it and replaced all manner of components to no avail. I still don't know what caused the problem, however, this is what eventually overcame it. I fitted a non return valve to the raw water inlet seacock. This completely cured the problem and had an additional benefit that I no longer had to keep replacing pump impellors. I had been changing these at least once a season and judging by the number of spare and part used ones onboard so had the previous owner. The current impellor has been in use for at least 6 years now and when I checked it recently, I simply put it back as there was no wear on it whatsoever.

 

[Beneteau381]

hi, I had exactly this problem when I first had my present boat, not a sail drive though. I tried everything to cure it and replaced all manner of components to no avail. I still don't know what caused the problem, however, this is what eventually overcame it. I fitted a non return valve to the raw water inlet seacock. This completely cured the problem and had an additional benefit that I no longer had to keep replacing pump impellors. I had been changing these at least once a season and judging by the number of spare and part used ones onboard so had the previous owner. The current impellor has been in use for at least 6 years now and when I checked it recently, I simply put it back as there was no wear on it whatsoever.

I remember an article in PBO about something similar. The cam in the pump was worn so reducing the pumping capacity. Also if the cam is worn, the face plates will be as well. The non return valve stops the poorly performing pump from losing prime.