1989 M80 Oil Injection temp sensor

[adid12]

I have a 1989 M80 oil Injection Mercury outboard.
It is on a Pontoon boat. The water from the pee hole is strong and cold. Whenever I am ideling everything seems fine, but when I get up speed the temp sensor sounds, then when I idel back after a while the sensor stops.
Is this a THERMOSTAT problem or water pump? Where can I go to get step by step instructions on how to replace either one?
Thanks!!!!!

 

[blackbox]

Re: 1989 M80 Oil Injection temp sensor

the motor acts like it has a popet-valve/thermostat problem. they are under the same cover. i think the best manuals are the "factory manuals" for your specific motor. you can order them from most dealers or on line.

 

[Silvertip]

Re: 1989 M80 Oil Injection temp sensor

I generally suggest that people check their local library for outboard service manuals. While they may not have one for your exact engine, they may have Clymer or Seloc which may cover an entire series of engines but they are good enough for a thermostat/water pump replacement. I would suggest you have a poppet valve (bypass valve) issue. A thermostat that is stuck closed would likely create and idle over heat. If it's stuck open it simply overcools the engine which would not trip the alarm. A bypass valve that is stuck closed would create the high speed overheat and if it is stuck open, it would also overcool and not sound the alarm.

 

[adid12]

Re: 1989 M80 Oil Injection temp sensor

Thanks for the Library suggestion. A manual is ~$40.