Replacing '94 40hp temperature switch

[wallihunter]

I posted an earlier message about a very muted steady alarm at times when I have been using my '94 Mercury 40hp tiller motor. Today I think I finally figured out the problem. In running the motor in the driveway I noticed the temperature switch coming out next to the #1 plug seemed rusty and corroded. I wiggled the wire and the muted steady alarm began to go off and water began to seep out of the temperature switch.
I tried to remove the temperature switch after taking out the spark plug and there is no way to get a wrench to the nut. What is the best way to remove and install a replacement switch?

 

[Texasmark]

Re: Replacing '94 40hp temperature switch

We just had a similar muted alarm on another hp engine. The switch is supposed to dead short when it activates, but something inside goes astray in some cases and instead of a dead short which produces the ear piercing alarm, you get this muted alarm.....when there is nothing wrong with the engine's temp.....not supposed to be getting an alarm. Ours read about 150 ohms. Replacing it solved the problem. Sounds like what you have.

Mark

 

[jebeebe]

Re: Replacing '94 40hp temperature switch

you may have to drill it out and use "ez-out" to screw it out. Be carefull not to drill in too far. It is a 1/8-27 thread as I recall. you can pick up a set of EZ-outs at any hardware or autoparts store.

 

[Texasmark]

Re: Replacing '94 40hp temperature switch

Don't know where you are, but our temp sensors are pellets, about the size of 2-3 dimes stacked on one-another, embedded in the water jacket cover with one wire (tan or tan/blue stripe). Little bracket holding them in with one screw holding the bracket in place. Nothing to drill out unless it is the screw holding the bracket.

Mark

 

[jebeebe]

Re: Replacing '94 40hp temperature switch

Don't know where you are, but our temp sensors are pellets, about the size of 2-3 dimes stacked on one-another, embedded in the water jacket cover with one wire (tan or tan/blue stripe). Little bracket holding them in with one screw holding the bracket in place. Nothing to drill out unless it is the screw holding the bracket.

Mark

Hi,
Mine is a 1/8-27 npt with a tan /blue wire going to a plastic block and joining a tan wire I believe. Must be a different year and 60hp thing.