[C38] Overheat False Alarm

[david at dlrfilms.com]

My engine is back to doing that thing where the temp gauge climbs, the
alarm goes off, but the engine itself is not even too hot to touch, and I
can stick my finger in the coolant without getting scalded.

This problem plagued our 2008 and 2009 Summer sailing, but wasn't too big
a concern because we never ran the engine for more than about 5-10
minutes.

Thought I had it licked before our passage to the Caribbean in Nov 2009,
and indeed, ran the motor for hours on end with no such problem.

But now it's back, and with the wind out of the SE, that means getting
back into the harbor is a long enough run to get the overheat false alarm.

IIRC, cracking the thermostat housing open would (usually) solve the problem.

The other thing I notice is that coolent is not following through the
overflow tube to the reserve tank. It's not blocked; it seems like there's
a air bubble that's keeping the coolant from flowing.

I remember something about running the engine, and then adding more
coolant after it burps or some such. I have my manual and will re-read.

Meanwhile, any helpful hints are much appreciated.