Overheat

[G-Daddy]

Boat is a Sportcraft 252 with a Mercruiser 350 Mag Engine that has been running great. Was on Chesapeake Bay for some striper fishing on April 30-May 1 with no problems. Held temp right at 160? just like it should. Towed her to Lake Ontario last weekend and the first time we dunked her the temp went to 225? in a matter of minutes. Limped back into the harbor by running and shutting down and drifting. Finally got a tow back to the launch. Raw water pump is pumping fine. Pulled the thermostat and ran the engine a few seconds and heard a squealing noise. Shut her down right away then. Guessing the engine water circulating pump has failed? Any other possibilities?

 

[G-Daddy]

Re: Overheat

Since we had no immediate plans needing this boat, I decided to go over the entire closed cooling system - replaced the thermostat and engine circulating water pump as well as having the heat exchanger cleaned and pressure tested, drained and replaced the coolant. We ran the engine using a water trough a couple of times yesterday ? she comes to normal temperature and stays there. Now we are ready to set up a full-fledged test run/fishing trip.