Hi all,
I'm considering moving my engine raw water strainer from just below water level to about 450mm above.
Why?? 2 reasons
1.Recently noticed a small amount of water in the bilge, tracked down the source to a split/fracture in the O ring for the lid on the strainer. I replaced the O ring, all good now. When I'm not on the boat the cooling water valve is closed, usually. I noticed this leak while enjoying an afternoon moored up near home, the water valve was open due to engine use. If it was above water level it would not have leaked.
2. You could find a more inconvenient present position for this strainer if you tried, it is in the way of everything.
This issue got me wondering???? Should the strainer be below water level or above? I can see pros and cons for both positions.
Is there a protocol, am I missing something?
Any thoughts, greatly appreciated
Mike

If your raw water pump is even slightly off par (worn impeller, dripping shaft seal etc) and/or there is even the tiniest air leak, the pump may not prime and will not deliver any water to the engine. That's a big price to pay for the occasional bend & stretch.
Also, I suggest you make it a rigid routine to close all thru-hulls every time you leave the boat. If they're hard to get to, drill a hole in the handle (for ball valves) and use threaded rod to make a remote closing handle that's easy to reach.
Cheers, Graeme

I have a related question. I mounted my seawater filter above sea level. When I open it to clean there's a good metre of water above the raw water pump that stays there, and there's 0.5m down to the seacock and that stays too, as long as sea cock is closed. So priming is ok for me.

But the engines sea water cooling flow is too low I'm wondering now if the filter was below sea level would the raw water pump get a bit of a head of pressure and boost the flow rate? It needs a heat exchanger clean too.

It's always best to follow the manufacturers suggestions. I think just above the waterline is best. Then the filter can be cleaned without shutting the seacock. As long as there is a reasonable length of hose in a loop down to the waterpump so water is always there to prime the pump the strainer can be installed anywhere you like. Does not matter if it's a metre or 2 from the waterpump.

I positioned mine directly on top of the sea cock with the strainer lip about 5 mm below waterline. This allows me to poke a metal rod or coathanger wire down through the strainer and sea cock to clear it if necessary. The height of the lip makes the strainer self priming.

I installed mine just below the waterline and about a 1.5 m from the pump. I wanted the plastic away from the engine heat and somewhere with instant access without having to remove engine hatches

Hi all,
thankyou for your replys.
it seems there's no hard or fast rule for the location of the strainer so I'm going to "let sleeping dogs lie".
Best wishes, Mike

I just happened to be looking at the Beta manual a few moments ago and they have the filter mounted just above the seawater level. The lid 50mm above the waterline. If I recall the Volvo installation manual had it in the same place. In the diagram they also have the pipe to the pump down in a loop well below the pump.