1981 Johnson 35HP Overheating

I purchased a boat with a 35hp Johnson on it. I took it out for the first time last weekend and everything was running fine. I thought I would take it around the lake and air the motor out. After about 10 minutes the engine shut off. I hit the key and it started right back up. I started moving and went full throttle again. I went about 100 yards and it shut off again. Once again it started right back up. This time I just went part throttle and went back to the boat launch. After I got the boat out of the water I took the hood off the engine and it was way too hot to touch. I know that I had an excellent water stream coming out of the back of the motor. Once I got home I took the hood off again and the motor was still too hot to touch after about a half hour of driving home. I noticed that where the coils mount to head were a little melted and the bolts appeared loose that hold the coils down. I talked to a local outboard repair shop today and I purchased a thermostat, gasket and a new head gasket right away. He was telling me that it probably isnt the thermostat but the water pump instead. I was wondering how it could be the water pump when I have an excellent stream of water. As for the cutting out he said there is a safety cut off in the ignition if the motor overheats. Is there any way to hook up an overheating alarm also on the motor and where could I get one? Thanks in advance.

Re: 1981 Johnson 35HP Overheating

Anyone?

Re: 1981 Johnson 35HP Overheating

check your waterpump the hot horn is shuthing the motor off

Re: 1981 Johnson 35HP Overheating

If it was my mtr I'd first check the water pump. Then as long as the coils started to melt I'd pull the head and check the water deflectors in the block. If they are swelled up they can cause the block to overheat from bad circulation. This can happen even tho' the pisser is working.

Re: 1981 Johnson 35HP Overheating

boobie said:

If it was my mtr I'd first check the water pump. Then as long as the coils started to melt I'd pull the head and check the water deflectors in the block. If they are swelled up they can cause the block to overheat from bad circulation. This can happen even tho' the pisser is working.

Click to expand...

+2.
I wouldn't run that motor anymore until you get it fixed.
Did the Thermostat and head gasket help?
Please keep us posted.

Re: 1981 Johnson 35HP Overheating

I got all the parts together today. I am going to tear it apart on saturday morning because I will have the house to myself and nobody around to bother me while I am working on it. Thanks for all the inputs!

Re: 1981 Johnson 35HP Overheating

Some other things should be looked at as well. Is your water intake clean or is it covered with either dirt or zebra mussels? Is there dirt in the hose that gets the water to the engine?
Take a hose and hook it up to the the tubing above the water pump,if the water flow is unrestricted that should be clean,if not,clean it.
Make sure the impeller is in proper working condition and make sure that it is installed according to the manual.
There are a few more common sense checks to do.Remember these outboards do not require rocket scientists to fix them,most things are just common sense.

Re: 1981 Johnson 35HP Overheating

Well I got the head off this morning and when I popped the thermostat out of the head I beleive I found the problem. You can see in the picture. I put the t stat in a pot of water and had it up to 190 degrees and it never opened. All of the deflectors looked good in the block. I replaced the thermostat, head gasket, and cover gasket. Had it running for well over an hour and I was checking it periodically with a laser temp gun and the engine never went over 139 degrees. I could even put my hand on the engine for quite awhile without burning myself. Hopefully this weekend Ill get it out on the lake and make sure everithing is good. Thanks for all the input and advice.

Re: 1981 Johnson 35HP Overheating

Sounds good. She should be good for another 30 years! Thanks for the update.