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Overheating alarms on a Yanmar.
What's the proper height of the sea strainer with respect to the waterline?
My 1980 C&C 34 (with a Yanmar 2gm20) has one of those standard bronze columnar sea strainers, with an input hose from the throughhull, and the output going right to the engine. Opening the strainer cover, I see water in the strainer, and the strainer itself is clear, yet I don't see a stream of water coming from the input hose connected to the (open) throughull.
This is my first time maintaining an inboard diesel, so pardon my ignorance, but how is the contraption supposed to work? Is the strainer supposed to be right below the water line and have raw water naturally gush in? Is the cover supposed to make a vacuum seal against the strainer, and the raw water pump is supposed to suck water up the few inches of hose from the throughhull into the strainer?
I find the latter unlikely, and feel maybe my strainer is mounted too high right now to adequetely supply the engine with water. I've always thought the amount of water coming out of the exhaust kind of paltry, but it hasn't thrown alarms until recently. I've checked the strainer before, and always found water in the strainer. I seem to recall at some point noticing that the water level seemed to come to right below where the input hose hits the strainer, meaning with the rocking of the boat I would see the level maybe rise up to feed the strainer.
Note, the impeller is in one piece and looks fine.
Thanks in advance.