1964 Johnson V4S-16 75hp overheating

[Reista]

I've been through the outboard 100%, removed powerhead and everything, and the engine now runs like a champ but will sizzle water away the second you drop some on it. Infrared meter says 280 cyl 2/4, 290 on cyl 1/3. I have the motor sitting in a big tub of water (i know better than to run it dry) and it looks like it's chugging air for some reason when I start the engine. It has a Evinrude 75453A lower end on it, and I'm 100% certain that the water pump is installed correctly. There's obviously something I'm missing here, any ideas?

 

[Reista]

Took out the Tstat and the check valve and flushed motor totally, didn't seem to be any blockages- tstat housing was 100% dry (still had a little sand stuff in it from the last run from the previous owner). It's too late to get a trial start without a tstat so I'll update tomorrow if anything happens. Aslo found out that having the intake in the water isn't good enough as the water pump isn't self priming - so gonna go with a bigger can

 

[Willyclay]

Some members have reported after-market water pump impeller bushing failures which might explain no water being pumped. Possibly the key that drives the impeller failed or became disengaged. Good luck!

 

[F_R]

You might get away with removing the vernatherm element and it's plastic valve from the thermostat housing, but if you remove the other plastic valve there is a direct air path down to the water pump and it won't work. Same thing if you run it with the t'stat cover removed.