Mercury 90 elpt 2 stroke overheat
 

Hey everyone
kind of unusual, runs fine and runs cool, but between 3800 and 4200 RPM trying to get on plane the alarm goes off solid beep, we unhooked the temp sensor and beeping did not happen, once on plane, she cools right off again, alarm goes away. 2003 vintage hours unknown, but has new plugs, impeller, poppet, carbs recently rebuilt, owner brought it back for a carb adjustment, we richened the idle air by a quarter turn, Idles and runs great plenty of power, has anyone had this happen?
only sets off alarm with a load trying to get on plane and goes away once over the hump.
sorry about first post spelling and grammer
thanks

scream and fly. we aint outboard gurus...

prob the oil tank sensor / switch assembly is going bad

its either you need the whole tank - on the motor side or the cap with the sensor hooked to it or the switch for it. These go bad all the time. You did not post your engine serial number to see exactly the set up.

I will add all Marine engines go off engine serial numbers. Year model means almost next to nothing for set up and parts used per marine engine app. Hate to sound like a broken record but I can not believe before I came up here no one made it point to bring this forth as to how important they are.. Engine serial numbers guys. .

example how it works as it does not go by year models with all marine engines

Mercury Marine 90 HP (3 Cylinder) Outboard Motor Parts by Serial Number Range

Do you have a GAUGE hooked to the temp sensor?
It would be helpful to know if you are actually getting an overtemp situation or just an erratic sensor signal.

As stated, many Merc control boxes have a single warning horn, which will sound on low oil OR overtemp with no audible difference.
I would need to see your specific engine wiring diagram to know for sure, but disconnecting the temp sender wire MAY also disable the low oil warning as well. Not sure.

MC