3.0 Mercruiser Still Overheating

JimS123

Fleet Admiral
Joined
Jul 27, 2007
Messages
7,952
Worked fine on the muffs and most of the first day's outing. Then came in a no-wake zone and docked at a restaurant when it started to overheat. Got up to 180 or so on my gauge.

Replaced the entire water pump and the thermostat. Next time out the gauge showed about 150-155, vs the 140 it had always run at. I spent an hour at various speeds and it never wavered, so the T-stat surely is holding it at a constant temp. Then, went in a no-wake zone for another trial and after about 5 minutes at dead idle the temp started to climb again. Bumped it up to 1300 rpm or so and the temp came right back down.

Could the original overheat have damaged the temp sensor that it is not showing 155 instead of 140?
Obviously, at 750 rpm its not providing enough cooling water. Is that normal?

This is a fresh water motor and I see no signs of internal corrosion.
 
Top