1980 70 hp. johsnon overheat alarm, is there one?

[Incaboater]

Just wanted to know if my motor has an overheat alarm? I have never heard it which could be a good thing or bad. The good one is that its not overheating and no cause for alarm, the bad thing is that its overheating and no alarm to tell me? The motor pees fine and I have had no problem with it. I was really more curious as to how to tell if this motor has an alarm and how to test and see if it works?

 

[F_R]

Re: 1980 70 hp. johsnon overheat alarm, is there one?

It has one. It is in the remote control and the sensor is in the cylinder head.

Look for a tan wire going to the cylinder head. There is a rubber sleeve covering the wire connector. Slice the sleeve back to expose the connector, turn on the ignition key, and touch the wire connector to bare metal on the head. You should hear a godawful racket from the remote control.

Please don't depend on the alarm to warn you of water pump wear. If the pump quits suddenly at full speed, as from a spun impeller hub, the powerhead will cook to destruction before the alarm ever has a chance to sound. Proper prevention is to replace the water pump periodically whether it needs it or not.

 

[Joe Reeves]

Re: 1980 70 hp. johsnon overheat alarm, is there one?

Yes, an alarm horn exists. If you're using a regular OMC (white) control box, the horn would be inside it. If you have a console type control unit (on top the dash/console, the horn would be attached to wires under the console.

To test the horn, have the Key in the ON position (engine not running), then find the TAN wire leading out of the cylinder head. Upon grounding that wire to the powerhead, the horn should sound. If it does not, find out why as that's the only warning you'll received before the engine seizes.

Note that the horn, when operating properly, sounds before the engine is hot enough to do any damage.