sea water raw water colling won't pump after sailing fast

[donradcliffe]

I've had problems with the seal in the vetus type strainers if they are mounted too high, solved with a smear of silicone around the top and under the nut.

[onavegador]

I had the same problem on my catamarans. When the impellers have been new installed the problem does not arise but after a few engine hours still as before. Raw water intake was through the saildrives. Instead of priming with filling the water filter (strainer) with water I always closed the seacocks of the raw water inlet and opened when I had to use the engine (s). Not an elegant system but it saved me many impellers.
Good luck
James

[Jim Cate]

We had similar problem on our previous boat. Changing the impeller didn't solve it. Noticed considerable wear on the inside of the cover plate. Cleaned the outside of the plate, lapped it on some fine abrasive cloth on a flat surface and installed it with the lapped surface inward. Complete cure.

Jim

[Rivatar]

I replaced that type of slotted strainer as cleaning sea grass from it was almost impossible. Try closing the thru-hull whilst underway, on my Bavaria the water pump is a long way from the thru-hull and it is easy to strip the impeller on starting up. Solution for me was changing the strainer.

[Suijin]

Guys he is talking about the "grate" installed on the hull surface over the inlet thruhull.

It's supposed to be installed like it is. Solution is either remove it, turn it around, try a different grate, or find a way to bleed the line leading up to the pump, which would be a serious kluge and PITA.

[patprice]

Where is the inlet fitting and new strainer located? On the centreline I assume. Is it deep enough? At high boat speed is it, due to heeling, sucking air?

[Bill Conlyn]

He did not say why to remove the scoop with the solid part towards the stern, main reason why is , while under sail, especially at your speed, that scoop will force water though the cooling system and fill the cylinders with sea water. Left alone you will see water running out of the engines intake.
I always use a round external strainer. Also I mount the internal sea strainer so the top is just below the waterline. Hope this helps.
Another thing, always check for water flow after starting the engine and if your exhaust outlet is below the water, move to above the waterline so it can be monitored while underway and at start up.

[datapete568b]

Southbay sea strainer We have a lot of seaweed the only strainer that works well in the great Southbay fire Island New York
Again only if it's the sea strainer housing that's at issue

[james247]

Had the same problem. It is an air lock caused by cavitation
Create a high point in your raw water at or about the water line and put an air bleeding valve in the line. A twist of the valve the air lock is released. Start the engine - no problem. Make sure the isolation valve is located before the airlock valve so you can Isolate the line when the boat is moored or in its marina berth.

[boatbod]

Worn pump body. Enough air gets by the sides of the impeller that it won't draw a prime. Once primed it will continue to pump just fine until air gets in again.

Replace the pump and the problem will go away.