1981 Evinrude 35 horse runs hot under a load

Seatex

Cadet
Joined
Jul 21, 2011
Messages
10
I posted here back last year in August and had several replies. Life got in the way and I've just now got back to working on this motor again. It runs fine in neutral at idle but starts to run hot when under a load. I bought the parts to change the thermostat and finished that today. The old thermostat came out in 4 pieces and there was sand wedged behind the cover plate gasket. I cleaned everything up and ran some weedeater line where I could and put everything back together.

I filled up my 40 gallon water barrel put the motor in and fired it up. The tell tale water ran about 80 degrees and a 2 foot strong 1/4" stream of water was coming out of the tell tale at the block.

Put it in gear and the tell tale water shot up to 125 degrees. Back in Neutral water temp drops back to 80 degrees.

I'm at a loss, It seems to be running hotter with a new thermostat, of course there was no thermostat with the condition the old one was in.
 

Cofe

Lieutenant Commander
Joined
Apr 23, 2009
Messages
1,883
Re: 1981 Evinrude 35 horse runs hot under a load

The thermostat is designed to open at 145 degrees. If the head temperature is staying at about 145 degrees when under load, everything should be fine. Taking temperatures of the tell tale water can be misleading, and having the motor in a barrel of water will heat up the water quickly. The ideal way is to put her out on the water and check it there.
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 1981 Evinrude 35 horse runs hot under a load

yea .. what he said..I would just add that if you had sand caked around the t-stat, you probably have sand all in the block..order a head gasket and pop that head off, clean it out.
 

Seatex

Cadet
Joined
Jul 21, 2011
Messages
10
Re: 1981 Evinrude 35 horse runs hot under a load

Thanks Cofe. I plan on getting out to the lake and running it around the ramp. A friend of mine has an infared temp gun i believe i can use when i go.
SparkieBoat - The sand was behind the excess gasket material behind the coverplate below each spark plug on the water jackets. The thermostat area looked clean.
 
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