470 mercrusier overheating

M

mhardy0000

Cadet
Joined
Aug 26, 2010
Messages
6
I have a 1981 mercrusier 470 that is overheating. When the engine is not in gear I can run the engine at 2500 rpm's all day and it dosent get above 150 degrees, as soon as I put it in gear and start to get up on plain it overheats to 240. I have changed the Impeller, checked all the hoses and water is running through them fine. Plenty of water coming out of the prop.
I am at a complete loss. Help :
 
B

Banditz

Petty Officer 2nd Class
Joined
Apr 21, 2010
Messages
168
Re: 470 mercrusier overheating

Remove the heat exchanger, then take off the plates on each end. Clean out the channels in there with CLR, and also make sure you install new fluid. Water and anti freeze. Then report back. Oh yeah, dont buy new gaskets unless you rip one. being rubber it can be reused. And dont torque the single nut bolt if you do you could end up bending the metal plate and then being forced to either replace or bend it back perfectly flat.
 
Bt Doctur

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,111
Re: 470 mercrusier overheating

Also check the power steering cooler for a clog, next would be the impeller in the drive.
 
B

Banditz

Petty Officer 2nd Class
Joined
Apr 21, 2010
Messages
168
Re: 470 mercrusier overheating

He stated he already changed out the impellor. Also the 470 is a closed cooling system.
 
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