100 hp right side overheating

[jman518]

I have an old crestliner trihull that I purchased a few years ago. Foolishly, I didnt check for spark and have already had to buy a new cdi box. Now that it runs good, the right side (looking at the motor from behind the boat) over heats when it runs. The left side on the other hand heats to temperature and then stops increaseing in heat. We have looked at the impellar and it seemed nearly new and had no dry rot. To be completely honest, I dont know much about boat motors I have always worked on cars, atvs and other small engines. If anyone knows possibly why this may be occuring please let me know. The motor is a 1972 100hp Johnson.

One thing that I was thinking is, does the motor have two thermostats? if so, is the right side not opening? Could the head gasket be bad? It has good compression.

Thanks,
Jason

[boats.net]

Could have clogged water passages, waterpump may not be supplying enough water to keep all engine cool. There is only one thermostat.

[jman518]

What is the best way to clean the lines out. I have an air compressor, would that be sufficient pressure?

[boats.net]

Yes the air compressor should have enough pressure.