I 987 johnson 120 overheating issue.

[kbmsound]

Ok, bear with me folks bit of a story to write here. So I had posted about my motor temp alarm going off. Now, I replaced the water pump and both thermostats. I went out yesterday, and to make a long story short, had to get towed in by the coast guard. After a few minutes of running I stopped at a spot to fish, and came time to leave, motor would crank but not start. I had a spare primer bulb, switched it, nothing. Eventually I depleted my batteries, not before noticing the main battery had very hot at the positive post. It actually blistered my thumb. So we get to the dock, I decided to attempt to start it for shits and giggles, and on the first turn of the key it started!!! I have a bipolar motor. I thought the batteries did not have enough juice to start it but I was wrong I guess. Any one ever experienced this before.?

 

[kbmsound]

No Title

 

[tblshur]

kbmsound, just a guess but if u have been use to starting the motor without functioning thermostats , normally u have to do a cold start every time u start the motor, after installing the thermostats u may have flooded the motor.i have a 83 140 first time of day i have to do a cold start but after that, i better not choke it , unless its like 40 or 50 degrees hope this helps :joyous:

 

[kbmsound]

kbmsound, just a guess but if u have been use to starting the motor without functioning thermostats , normally u have to do a cold start every time u start the motor, after installing the thermostats u may have flooded the motor.i have a 83 140 first time of day i have to do a cold start but after that, i better not choke it , unless its like 40 or 50 degrees hope this helps :joyous:

I replaced the thermostats in an attempt to solve the temp issue together with water pump. Alarm keeps going off. I put my hand on the tale tale while alarm was going and water was hot but not to where I could not keepossibly my hand there. Also, why was the battery so hot? I literally got a blister on my fingers. After an hour of being off, the motor turned on like nothing, even when I thought batteries were dead.

 

[sutor623]

Battery gets hot when rectifier/regulator goes bad. This can also lead to stator failure. That also explains why the motor wouldn't start when hot. Bad stator will normally rear its head when hot.

 

[sutor623]

Google Joe reeves small rectifier test and test it. Also look for black goo coming from under the flywheel. Check battery for voltage, and check the voltage when engine is idling.

Get an infrared thermometer and check heads when alarm is triggering. If the heads aren't overheating, check/ replace temp switches in the top of the heads. If that doesn't turn out to be the issue check the blocking diode in the wire harness.

 

[James R]

You are apparently running in salt water A dirty corroded battery connection will cause the wire and terminal to heat up. If the motor is not actually over heating disconnect the temp switches at the heads and see if the alarm turns off . If it does you have your answer.

 

[kbmsound]

Google Joe reeves small rectifier test and test it. Also look for black goo coming from under the flywheel. Check battery for voltage, and check the voltage when engine is idling.

Get an infrared thermometer and check heads when alarm is triggering. If the heads aren't overheating, check/ replace temp switches in the top of the heads. If that doesn't turn out to be the issue check the blocking diode in the wire harness.

Will perform all these tests. Thanks.

 

[kbmsound]

You are apparently running in salt water A dirty corroded battery connection will cause the wire and terminal to heat up. If the motor is not actually over heating disconnect the temp switches at the heads and see if the alarm turns off . If it does you have your answer.

The battery terminals are all clean and free of any type of build up.

 

[kbmsound]

Yesterday I took off the water jackets and cleaned up up of the slat deposits the best I could. The actual heads were not terrible but still cleaned them up too. While doing this, i checked the spark plugs and they didn't have signs of water going into the cylinder, they were just black with a little oil. Haven't got a chance to go out again,and I have a set of temp gauge kits and a water pressure kit coming. I will wait until I install and then go out to see want kind of readings I get. I will also perform the rectifier test. As far as the black goo from under flywheel, I can't remember seeing any, but will check to make sure. I am on duty today so I will do all these tomorrow. Thanks, all.

 

[kbmsound]

You are apparently running in salt water A dirty corroded battery connection will cause the wire and terminal to heat up. If the motor is not actually over heating disconnect the temp switches at the heads and see if the alarm turns off . If it does you have your answer.

I will do this as soon as I can go out again. If I do it with muffs the motor does not overheat.

 

[racerone]

Take starter apart for inspection / cleaning / new brushes.---Easy to do.---Have a good look at the battery cables , they may be corroded internally.

 

[kbmsound]

Take starter apart for inspection / cleaning / new brushes.---Easy to do.---Have a good look at the battery cables , they may be corroded internally.

Starter is fairly new. But will look at ithe just in case. Good idea to replace battery cables. Thanks.

 

[kbmsound]

Question: does the 87' J120 have a fitting for the water pressure on top of the heads or do I have to go the telltale route?