1978 85hp Evinrude overheating

[MadtownChris]

1978 85hp Evinrude fairly well cared for over the past 8 years I have owned it.

First time in water this year motored about 100 yards and the overheat alarm went off. I had previously tested in my driveway and the pee stream worked and the thermostat valves worked.

Back in the driveway I removed and tested thermostatic valves and they open at around 170° on my stove.

Interestingly, the water tubes leading to the thermostatic valves were bone dry after the engine overheat. So it seems no water got to the valves during the incident.

So I ran with the tubes disconnected and water seems to pour out rather thoroughly as you can see in the attached pictures. One is at idle and one is with the fast idle on. if I put my thumbs over the tubes and prevent the water from coming out, it warms up then I can take my thumbs off and out it pours and then everything cools off.

Impeller was replaced last year and ran well after replacement.

Do I replace the valves? Do I just put it all back together and hope for the best? Do I run without valves as my outboard guy suggested once?

 

[saltchuckmatt]

Yes....run without, flush well install new ones and test head temp with hand or IR gun.

Report back, salt use or no?

 

[MadtownChris]

Freshwater

Also I put in at a sometimes goopy launch though I didn’t see any vegetation that looked like it would clog the intakes.

 

[saltchuckmatt]

Flush, flush.

Mud dobbers?

Flush.

170 is to high I think. Others will know.

 

[MadtownChris]

No mud dobbers (at least not many) around here. Interestingly I think you are correct about the temp. The ones I ordered say 143 degrees. But they're identical parts and shop to the ones I measured at 170. Maybe they start opening at 143 and fully open higher. I didn't carefully observe.

 

[saltchuckmatt]

No mud dobbers (at least not many) around here. Interestingly I think you are correct about the temp. The ones I ordered say 143 degrees. But they're identical parts and shop to the ones I measured at 170. Maybe they start opening at 143 and fully open higher. I didn't carefully observe.

Motor shouldn't be over 160, at least at idle.