1990 70hp Johnson Overheat Alarm

[Mandoman]

I have a 1990 Johnson 70 hp. I have been having trouble with the overheat warning and shutdown. <br />At the suggestion of my mechanic and in order to remove potential problems I took off <br />the vro auto oiling feature and I am now premixing the gas and oil 50:1; I've replaced <br />the impeller and there is a strong discharge stream; the head gasket was also replaced when the engine was checked for cooling restrictions; In order to monitor engine temp I installed a temp guage. The engine seems to run well at between 2000 to 3500 rpm and will run at a higher rpm without a load on the engine. The problem starts when the engine is going over 4000 rpm under load. The last time I ran the engine <br />(Saturday) the temp gauge was reading about 80c or 176f when the alarm wentoff and the engine shut down. The manual I have doesn't identify the proper operating temp., so I am not sure what normal would be. Does anyone have any thoughts as to the problem ?

 

[outdoorwood]

Re: 1990 70hp Johnson Overheat Alarm

stator overheating...this is deja vu to the word for me. <br /><br />the stator gets hot, sets off the alarm, the alarm won't let the motor run. the motor itself is not running hot.

 

[seahorse5]

Re: 1990 70hp Johnson Overheat Alarm

There were a series of service bulletins around that time, new improved water pump kits, and relocating the tell-tale water fitting to the top of the exhaust cover. Around that time there was a change to the temp alarm sender that kept giving false overheat signals. See a knowledgable dealer who will look up those bulletins for you and get you running like it should.<br /><br />The max operating temp is 165 F.

 

[clanton]

Re: 1990 70hp Johnson Overheat Alarm

Check your pig tail (wire) on the temp sensor, should be about 7 1/4 inches long tan with blue stripe, if yours has only tan wire, it is wrong sensor. It will not stop your overheating, but when it sets the alarm with the correct sensor, it will realy be hot, the sensor is set at 240 degrees F. The tan wire sensor set at 203 degrees F.

 

[Mandoman]

Re: 1990 70hp Johnson Overheat Alarm

Thanks for the info. I will check it out tomorrow and let you know what I find.

 

[boatin]

Re: 1990 70hp Johnson Overheat Alarm

Dont guess there is a web site that shows service releases or recalls for a particular motor???

 

[seahorse5]

Re: 1990 70hp Johnson Overheat Alarm

Here is a list of bulletins that someone posted a while back pertaining to the 3 cylinder motors with overheating problems. Have your dealer look them up for you to see if they apply to your particular motor.<br /><br />60 & 70 hp service bulletins for cooling and overheating<br /><br />SB 2221 Temp sensor new sensor pn 584166, tan/blue stripe wire.<br /><br />SB 2225 thermostat seat new seat pn 336416, may not need this in fresh water.<br /><br />SB 2271 jet and timing kits ds<br /><br />SB 2276R1 relocate tattle tale nipple to top of block.<br /><br />SB 2276R1 and new pressure relief springs comes in waterpump kit pn 432955.