Re: 76 model 70 hp overheating
I ran my 70 hp engine until it lockup. The overheating alarm did not sound and i did not know water was not getting to the engine. Now I want to check compression 1st what should the PSI be? Also could a stuck thermostat have stopped the water flow because the water pump is fairly new. Are there any other parts that can block the water flow?
There is no set compression numbers in the OEM manual due to the variables of the compression gauge being used, engine temperature, cranking speed, etc...
With my gauge and a good battery I get 130 or so psi on each of my cylinders. General rule of thumb is that they should be within 10% of each other high to low...
As far as the thermostat stopping water flow, the thermostat could stick shut, but I believe your engine also has a high speed water flow bypass which diverts the water flow around the thermostat at high speeds (hence the name) so if you thermostat was stuck then the high speeds should open up to permit flow. Also the early three cylinders are notorious for air pockets in the water jackets. So many people modify the engine to have a tell tale / air bleed at the top of the engine to keep this from happening as OMC incorporated it into the design of the engine in 1979 or 1980...
If you search this forum people have posted the technical information on how to do this modification right from the original OMC paperwork...
HTH...
Billy
