'83 7.5HP Johnson Running to hot with tstat and ok without

[merc20076]

I was working on my Johnson 7.5HP today. I changed the head gasket and used some sealer. Put in also a new thermostat kit and once all done I test it in the 60 gallons drum.

Motor did not work good for long, it started getting hot fast even with a good stream of water coming out from the pee hole. I shut it off, once it got to hot on the head before blowing up the new head gasket.

Got the tstat off and it ran #1, strong in gear and a good idle . But is this ok if I will do a lot of trolling with my new inflatable boat. I have a 4.5HP Johnson and they dont run with one.

By the way, the impeller is new also. What can cause this?

 

[fireman57]

Re: '83 7.5HP Johnson Running to hot with tstat and ok without

Sounds like you installed the tstat backwards. You can run it like that but it will like fuel as it will always be running cold.

 

[merc20076]

Re: '83 7.5HP Johnson Running to hot with tstat and ok without

That's wierd, I follow this diagram to install it. I can also try the other way.

 

[fireman57]

Re: '83 7.5HP Johnson Running to hot with tstat and ok without

I have bought a tstat that was bad before. They can be tricky to install with the spring and stuff. It's easy to get it a little crooked. Make sure that there is no gunk in the hole to stop it from opening.

 

[Cofe]

Re: '83 7.5HP Johnson Running to hot with tstat and ok without

When you changed the impellers, was the old impeller chewed up? If it was, impeller shratnel may have been pumped up the water tube and into the power head and lodged somewhere. I have found impeller trash in the water passages around the cylinders, exhaust cover ports, under the powerhead, and in the powerhead.
As was mentioned, new thermostats can sometimes be bad. It is a good practice to heat some water on the stove with a candy thermometer, and test stats before installing.

Sealers like silicone can get stuck in a thermostat also.