1978 evinrude 70hp model 70873 problem

[benny1996]

running a bit too hot (+/- 20 degrees F); good that compression is even, but it is low.

Think my thermostat is causing it to be too hot? I ordered the one it says in the service manual but the hole/area the coolant passes thru seemed smaller than the one that was in it when I got the motor (that was stuck open) also do you think overheating is causing it to Rev up like that?

 

[Scott06]

Think my thermostat is causing it to be too hot? I ordered the one it says in the service manual but the hole/area the coolant passes thru seemed smaller than the one that was in it when I got the motor (that was stuck open) also do you think overheating is causing it to Rev up like that?

Over heating is influenced by-

condition of water pump impeller
Thermostat operating correctly
clogged or corroded water passages that may impede flow

if I recall correctly these motors have a telltale water port should have a strong stream of water coming out if week you are likely not getting enough water flow

 

[benny1996]

Over heating is influenced by-

condition of water pump impeller
Thermostat operating correctly
clogged or corroded water passages that may impede flow

if I recall correctly these motors have a telltale water port should have a strong stream of water coming out if week you are likely not getting enough water flow

Yeah the whole waterpump assembly is about 2 weeks old and the stream out of the tell tale is like a water jet. The thermostat is evinrude brand and I out it in 150⁰ water before putting it in the motor and it operated correctly

 

[oldboat1]

Don't know if you boat in fresh water or brackish, but consider removing the cylinder head cover, and cleaning out the water passages around the cylinders (old hacksaw blade works well). Refinish the mating surface of the cover using sandpaper on a hard surface, moving the head around in a figure eight pattern until shiny all around. Use a fresh gasket for reassembly and torque to specs working in circles from the center out.