72 Johnson overheating

[DanLieffring]

My 72 Johnson 40 horse (model 40EL72E) overheats. Was running fine all morning, and overheated in the afternoon. I checked the impeller, and copper piping, and that all looks good. Re-started it in my garage, in a barrel of water, and it overheated almost immediately. Is there a thermostat on this model? What else should I be looking at?

 

[tashasdaddy]

Re: 72 Johnson overheating

man, i don't even want to talk about, i've got a 71 50 hp driving me nuts, running hot. it's eaten 2 new impellers, and a housing. go here and follow the prompts to your engine diagram and parts list.
http://www.evinrude.com/en-US/Accessories/Literature/

 

[DanLieffring]

Re: 72 Johnson overheating

Thanks for the website.

I'm still a little lost as to where I should start looking to solve this problem. Any suggestions?

 

[DanLieffring]

Re: 72 Johnson overheating

I was told the impeller hub might be spinning around the splines. I will check that out, but want to know how to make sure all the piping is free of debris. How do I do this?

 

[Scaaty]

Re: 72 Johnson overheating

Thing been run in saltwater? Have a 2hp Rude in the shop right now shooting steam...everything else fine (had to grind the L/U bolts off to get the lower off..its a salted mess I bet inside, and bet I snap a few bolts getting the head off too)

 

[tashasdaddy]

Re: 72 Johnson overheating

i got mine clear up. with the lower unit off, attach a water hose to the water pipe on the motor, turn water on low, start engine with lower unit. you will be able to tell when the tstat opens. i replaced my thermostat, and poppet valve, and another impeller, every thing is now fine.

 

[DanLieffring]

Re: 72 Johnson overheating

My boat runs in freshwater.

I was told there is no thermostat on this model (40EL 72E). Is that true? It was my first thought that there must be a thermostat. Where is that typically located?