1979 Mercruiser 888 Ford 302 closed cooling system overheat

[ismo]

Boat stored for 10 years under cover. Got it running hooked up to ear muffs. It ran for 15-20 minutes, water temp 140-160. Thought all is ok. Put in the river, ran at dock for about 5 minutes. Smelled antifreeze , it was coming out of the overflow. Shut it down, took it out of the water thinking impeller was bad, but turned out to be ok and servicable. I will replace it anyway. What would be the next recommended direction to go?

 

[alldodge]

Boat stored for 10 years under cover. Got it running hooked up to ear muffs. It ran for 15-20 minutes, water temp 140-160. Thought all is ok. Put in the river, ran at dock for about 5 minutes. Smelled antifreeze , it was coming out of the overflow. Shut it down, took it out of the water thinking impeller was bad, but turned out to be ok and servicable. I will replace it anyway. What would be the next recommended direction to go?

After sitting for 10 years I would suggest draining the system and flush it. Pull the thermostat housing and inspect/replace the thermostat. Pull the exhaust elbows off the manifolds and check them.

 

[Volphin]

Sounds like the heat exchanger has scale build up. A radiator shop can fix that for you... or replace it with a new one.