Heat alarm sounding

[petryshyn]

How do you know its not overheating? Does the alarm sound if you disconnect the temp switch?<br />

better boating!

 

[clanton]

Re: Heat alarm sounding

What color is the temp sensor wire, should be tan with blue stripe. When overheated should go into S.L.O.W.

 

[ecd04911]

Heat alarm sounding

I have a 89 Johnson 60HP, after running anywhere from 15 min's to 3 hours the 'overheat'alarm sounds steady. After shuting engine off for a couple of min's we can restart with no alarm. Will then repete again after running (no set amount of running time). Water and oil flow is fine. Have replaced thermostat, didn't help. Motor isn't overheating even though alarm sounds. Mechanic can't determine problem as it never sounds when at the shop even after running in tank for extended period of time. It's driving me and family crazy. HELP!

 

[kenthrussell]

Re: Heat alarm sounding

hi had the same problem with a 200hp merc it was driving me crazy too,what i did was remove the sensor and get a digital thermometor (thermocouple type is best) and get a pot of water on the stove and heat on low, now what you have to do is hold the sensor at the bottom so the body of the sensor is grounded and get an ohmeter on the wire and bring the heat up slowly and see what temp the sensor closes or completes the circuit ,it will show you on the ohmeter,it should be around 190 degrees as the t-stats open at around 175, mine was intermitant and i replaced the sensor for 30 bucks and now it works great as ihave found out when the intake sucked some weeds up, or just buy a new sensor for 30 bucks and save the testing sounds like this is your problem...

 

[clanton]

Re: Heat alarm sounding

See Service Bulletin 2221, 2225, 2276, and waterpump kit pn 432955.<br /><br /> The 200 Mercury thermostst opens at 140/145 degrees.

 

[kenthrussell]

Re: Heat alarm sounding

clanton thanks a typo on my part thanks again for the correction