Mercruiser 1981 Bayliner runs hot at high speed.

[RandyJ]

I haven't even put it in the water yet! I just horse traded for this little honey and the guy I got it from said it runs hot when he opened it up and tried to plane out but stays cool when just chugging around. He got it from a guy in Florida who trashed the lower unit in a sand bar. Also he had replaced the exhaust elbows....said they were just crumbling to pieces. Just wondering how you guys would attack this problem. Supposedly this is a 1981 Bayliner Monterey (Cabin cruiser) with a 305 Chevy and 470 outdrive. Other than looking for trash in the cooling system I don't know where to start diagnosing. It shoots out plenty of water when the hoses are disconnected and I have installed a new engine water pump and outdrive impeller. I read something about alpha's could have similar problems if exhaust elbow gasket is improperly installed....but I don't think that is the case here. Any input would be appreciated.

 

[Trent]

Re: Mercruiser 1981 Bayliner runs hot at high speed.

My bet is you have the three inch heat exchanger? Those three inch exchangers were found to be too small and would overheat. You can try to flush out the exchanger but my bet is you need the new four inch exchanger.

 

[RandyJ]

Re: Mercruiser 1981 Bayliner runs hot at high speed.

Thanks Trent... Got a pair????

 

[RandyJ]

Re: Mercruiser 1981 Bayliner runs hot at high speed.

Trent...et.al.... I think I found the problem and wonder why it didn't run hot all the time. I pulled the thermostat housing block off and it was practically rebuilt with JB weld. It has rusted so bad from the salt water in the gulf coast that the only iddy biddy hole for the fresh water to get into the engine was totally clogged. I'm not sure how it even got water in the engine to cool it at all. It ran at 180 deg on a hose pipe. The thermostat housing was so rusted that I poked around on it with a screw driver and now have a hole bigger than a quarter in the bottom of it...which I'll repair with JB weld until I locate another one... hopefully someone will read this and feel sorry for me and donate one of those jewels to me... by the way, anyone got an idea of how much gas the tank will hold? I bet it's one of those whopper 80 gal tanks.

 

[RandyJ]

Re: Mercruiser 1981 Bayliner runs hot at high speed.

HA! I found the i.d. plate on the gas tank...only 64 gallons... that's a helluva difference from the 6 gallon tanks I'm used to and I can only imagine paying the lady at the convenience store when I fill her up for the summer on the lake.