 1972 Evinrude 50 hp overheating.
I recently purchased a long stored fresh water only 1972 Evinrude 50 hp model 50273C.
We changed the water pump as a result of the overheat alarm sounding after 5 minutes at idle on initial start up. It still sounded the alarm after the replacement of the pump.
Today I pulled the water jacket cover on the back and changed the thermostat which when tested did not open at the correct temperature. I also tested the replacement thermostat which functioned correctly. In addition, I replaced the "poppit" valve grommet. The valve was ok.
The unit still sounds the alarm. A temperature check of the head at the time it sounds the alarm (around 4 to 5 minutes at idle on the muffs) shows the temp to be 102 deg. Centigrade (215 deg. Farenheit) which per my clymer manual is the appropriate temp for the sensor to close and power the alarm horn.
I can tell when the thermosat opens as the water flow from the hub increases and steams. There is no tell tale trace on this model engine. As a result I "think" the pump is functioning correctly. I do not see any water coming from the upper vents at the top of the exhaust housing just below the engine.
My question is NOW WHAT??? Could it possibly be that this engine will not run on ear muffs? As I recall I had a similar year model about 30 years ago and ran it on muffs but I'm not certain.
Can I pull the head without removing the water jacket cover to check the cooling passages? Just where do the cooling passages run?
If anyone has a coolant flow diagram for this engine I would sure be grateful if they would post it for me.
Steve | 
