Over heating 175 '83 Johnson, Need help please

[viaqua]

I have a 83 175hp Johnson, no VRO. I replaced the impeller one year ago. The first trip out this year the horn sounded after about 500 yards of running @4000 rpms. I instantly killed the engine and waited for it to cool, ( it took about 15 min), then slowly went back, changed the thermostats, and the same thing. The pee stream is strong. It looked pretty clean behind the thermostats. The fuel is clean and is mixed 50/1 with stabill and ring free. I have not had the heads off since I have owned it for 12 years. It is used in salt and flushed after every use. What could be the problem?

 

[kenmyfam]

Re: Over heating 175 '83 Johnson, Need help please

I would back at the impeller again to begin with. You never know. How is it on muffs ?? plenty of water coming through ??

 

[jonesg]

Re: Over heating 175 '83 Johnson, Need help please

Take a look at the compression, a head gasket problem can overheat an engine, this assuming your water pump and therms are good to go.
Also look at water deflectors.

 

[viaqua]

Re: Over heating 175 '83 Johnson, Need help please

Thanks, I'll get some gaskets and pull the heads. I'll let you know the outcome.

 

[emdsapmgr]

Re: Over heating 175 '83 Johnson, Need help please

When on plane, the pressure relief valves in the thermostat housing open up to provide extra cooling water. When you replaced the thermostats, how did these valves look? Would be nice to know if you suffered an overheat on one side of the block, or both sides of the block. A laser temp gun is handy for this diagnosis.