Strainers to protect from failed impellers

[HoppySailor]

We recently purchased a Cabo Rico 34 with a Yanmar 3GM30F engine. The seawater strainer for engine cooling is between the through hull and the seawater cooling pump. I've read horror stories about impellers failing and having to pick bits of rubber out of the cooling system so I was investigating getting a simple strainer to insert on the outlet side of the seawater pump to catch the impeller bits before they reach the heat exchanger. As I was thinking it through, I got to thinking about the impeller in the pump on the closed side of the cooling system (anti-freeze side). A failed impeller there and impeller bits can end up in the engine cooling passages. Anyone install strainers on the downstream side of either of these pumps? Am I over thinking this?

[Jim Cate]

Ron, in most engines the freshwater circulating pump is not a rubber impeller type, so it isn't an issue. A strainer in the raw water side after the pump isn't a bad idea. I think that it should be large enough that a few blades wouldn't block the flow too much -- the combination of lower pressure due to missing blades and additional restrictions in the piping would lead to overheating quickly.

Cheers,
Jim

[HoppySailor]

Thanks Jim. I assumed that the freshwater pump also used a rubber impeller. I just had a look at the Yanmar service manual and the frehwater pump does not appear to use a rubber impeller. I'll just proceed with a strainer after the seawater pump. Thanks again for your help.

[c.spots]

I installed a screen just downstream of the seawater impeller. I couldn't find a large mesh screen, so drilled holes in the screen to assure good water flow. It has a clear window, and I painted the inside yellow - to make it easy to see any impeller bits. I don't know, but suspect that impellers fail a blade at a time, so when I see any rubber bits, the impeller gets changed.

[delmarrey]

If you're that paranoid I would put in one of theses.....



But in think it's over kill. If you change out the impeller on regular maintenance schedules there shouldn't be a problem. Over heating can cause failures too. So if you forget to open the seacock, replace the impeller too.