On Wed, 14 Mar 2007 22:31:17 GMT, "RG" wrote:

But if the engine checked out with a heat gun as you say, confirming a
normal reading on the helm temp gauge, it wouldn't seem to be an overheat
problem caused by impeller bits or any other cooling system malfunction.

Yes. Changing the impeller is probably a good thing to do but I'm
going to be surprised if it actually fixes the problem. I had the
boat out for an hour at lunch time today, never running over 1400 RPM
or so since I was in the local canals. No alarms of course.

The closest Mercruiser mechanic has a new ECM cable on order, should
be in next week. Hopefully there is a record of the alarm trips in
there.