Suggestions to investigate overheating problem in 1989 Johnson 30hp?

OttawaPhil

Petty Officer 3rd Class
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Aug 20, 2015
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85
I got a good deal on a CJ30ELEC (canadian version of J30ELECS).
I tore it down and tried to rebuild anything that needed it.

inspected piston and rings looks great. Rebuild gear case with seals and oil, rebuilt water pump with kit, rebuilt carb with kit, everything else just cleaned and reassembled with new gaskets and stuff.

Took it out for a half dozen times fishing. Starts right away and runs great at idle all the way to full throttle. Then went out for a blast down a river at full speed. After about 25 min at full throttle it shut down from the heat protection with some steam coming out of it. Obviously overheating. Let it cool some, then could start it and head back toward dock. Could not really get on plane all the way as more than 2/3 throttle would start it climbing too hot. There is warm water coming out the "pee hole".

So what can I check? Perhaps I screwed up the water pump build, I have never done one before. But, is there anything else you can suggest to check first? Getting the water pump on is a pain in the ***, rather do any other easy checks first; then can still do the water pump after if it needs it.

Thank you very much for your help,

Phil
 

OttawaPhil

Petty Officer 3rd Class
Joined
Aug 20, 2015
Messages
85
Oh, and I forgot to mention, I put a new thermostat in too while I was rebuilding it.
 

BrettNC

Petty Officer 1st Class
Joined
Feb 6, 2005
Messages
298
I would check for: A clogged or stuck cooling bypass valve, obstruction in cylinder block water jackets (remove cylinder heads), make certain that water pump isn't leaking.
 

OttawaPhil

Petty Officer 3rd Class
Joined
Aug 20, 2015
Messages
85
No Title

I took the head off and did not see any problems in the water jacket. I check the thermostat operation on the stove in a pot of boiling water and it appears fine as well. I took the water pump apart and it looks OK inside. What is this black piece on top of the water pump for? I seem to have broken it when I installed it into the top half of the motor. .

Would that cause the overheating?
Thank you for your help!
 

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OttawaPhil

Petty Officer 3rd Class
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Aug 20, 2015
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85
No I put it it backwards and forced it together with the bolts. Anyone know the answer about what it is for?
 

jakedaawg

Rear Admiral
Joined
Jun 26, 2012
Messages
4,275
It may be to keep shift link connector from rubbing on drive shaft. Same with water tube. Or it may direct the little bit of water that comes out of the top of the pump housing. Always wondered my self and never gave it much thought.
 
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