Trai wrote:
Some advice on where to look next would be greatly appreciated. I have
a Yanmar 2GM diesel engine that stops pumping water through the
cooling system after I have been out sailing for the day. To get it
started pumping again; I need to let the boat sit flat in the water
for about an hour. I have changed the impeller, but still have the
problem. The only time this seems to happen is when I have the boat
heeled over for a few hours.

Trai, use Google to search rec.boats.cruising via the Groups section using
the keywords: yanmar overheating jeffrey. Read the thread (there are
several, but you're about at the point I was, so you can probably skip
everything I went through prior).

Apparently this is not a rare issue. Many insightful and helpful comments
and suggestions were posted by the many knowledgable people here.