Just got an email from the maintenance crew who looked at the engine
situation.... interestingly, we did check the coolant level, which was fine.
So, whomever said the impeller, was dead on...

(edited slightly) The engine lost coolant (which was the consequence of an
overheat situation earlier in the month) and was running hot (in the
185-190+ deg range), which was enough to activate the over-heat alarm and to
still run "as if the alarm was a false negative." The raw-water cooling was
working, but the blades of the impeller had been deformed causing the
quantity of cooling water running through the heat-exchanger to be
insufficient to cool the engine to within it's operating temperature range,
thus causing the alarm.


We will routinely replace raw water impellers in all overheating situation
in the future, as well as positively check the flow of raw water cooling
throughout the complete system: through-hull to mixing elbow.

--
"j" ganz @@
www.sailnow.com