|Normally, there has been a substantial flow of water from my exhaust, but this season, there didn't seem to be as much splashing and spluttering as usual. No temperature warning, but the flow seemed off the pace. Looked at the impeller - no problem there. No leaks, either. Fortunately I remembered that the engine seemed to take a long time during its first start after launch to begin expelling water. That was the clue; the engine wasn't sucking water from the lake with its usual thirst. I took the cover off the water strainer and found that the gasket had semi-perished and compressed to the thickness of a sheet of airmail paper. No longer doing its job, it was allowing a small amount of air into the strainer, compromising suction of water into the strainer and then to the engine.
The solution was to buy a small sheet of rubber (about 1.5mm thick), trace then cut out the shapes of the strainer cap and its retaining nut/washer. With installation, problem solved.
C&C 27 Mk IV