1989 120hp Johnson Overheating

[noclaim]

Model 120TLCE. 225 hrs.This was posted Oct. 26th but lost. Water pump ok. Telltale ok. Used in salt water, flushed in fresh water. Warning horn sounds over 3000 rpm and temp. gauge shows hot. Shut down and let cool and runs ok below 3000 rpm. I think it is the thermostat. Any opinions and suggestions on replacing or does anyone have a manual?

 

[ob]

Re: 1989 120hp Johnson Overheating

JamesE, go to bottom of page for manual.I believe the lower thermostat cover on your particular motor is a pain to remove but some choice words should get it done. Check with dealer on new t/stats as some of the springs and assys. have been changed from original.

 

[Walker]

Re: 1989 120hp Johnson Overheating

That is a looper motor right. If so then the T/Stats are on the back of each head up near the top. Look for a small cover on each head with 4 bolts holding it on.

 

[noclaim]

Re: 1989 120hp Johnson Overheating

I guess it is a looper it has a large bulb on the back of the powerhead. Thanks for your answer.

 

[Solittle]

Re: 1989 120hp Johnson Overheating

James - don't know if the large bulb identifies it as a looper - - On many of the OMC motors of those years the bulb was for the highest hp for the year. For example the 79 115 hp had a flat plate, the 140 had the bulb.<br /><br />I have 1988 OMC V4s and ob is right on about the cussin. The nastier the words and the louder they are uttered will make the job easier and go much quicker. I did both my motors this year - a real bit%h & glad they are done.<br /><br />I would not even think of trying without a manual. Beware some OMC mechanics will tell you that you have to pull the powerhead to get access (one guy told me $250/motor). Not so as can be done by dropping the pan if you have the right wrenches.

 

[Dhadley]

Re: 1989 120hp Johnson Overheating

The 89 looper style thermostats were pressure controlled and on the top of each head. If they are the white ones you need to change them to the black ones. You can also upgrade to the 93-94 spring style by changing the thermostat assy, new spring and cap. Then you can get rid of the throttle control pressure valve.<br /><br />Good luck!

 

[drothman]

Re: 1989 120hp Johnson Overheating

James E.<br /><br />I have a 1991 120 Johnson. Wonderful motor, but I had intermittent overheating problems with mine for a while. The thermostats sit on rubber donut seats in wells at the top of each cylinder bank. One of the donuts was sitting cockeyed in the well. When I corrected that (really easy job), problems over. I expect yours has the same donuts- make sure they are properly seated. Good luck.

 

[noclaim]

Re: 1989 120hp Johnson Overheating

Thanks to everyone that responded. Just so you know, the thermostats are on top of the cylinder heads as suggested and I replaced them for $36.00 each with improved versions (per the dealer) and now working fine. I did purchase an OMC shop manual from the dealer.

 

[Dhadley]

Re: 1989 120hp Johnson Overheating

Thanks for the update. Its always nice to know how things worked out.<br /><br />Now get out there and use it! Lol!!