I have a 90hp 2003 Mercury. The last few times out the overheat or low oil alarm starts going off right at 21mph on my gps. My tach hasn’t worked in years. If I drop down to 20mph it instantly stops and above 20mph it starts again. If it was overheating it would be so instant and same thing with the oil level. Other than the alarm it runs perfect. Water pump was replaced a year ago, along with thermostat and poppet valve. Any ideas?
ONLY 2 THINGS ON THAT MOTOR CAN ACTIVATE ALARM
OIL AND TEMP
YOU ARE GOING TO HAVE TO DO SOME DIAGNOSTIC WORK TO ISOLATE.
USUALLY THE OIL ALARM IS INTEMITTANT (BEEP BEEP BEEP BEEP)
THE TEMP IS CONSTANT (BEEEEEEEEEEEEEEEEP)
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on mine the manual says it is a constant alarm for both. I’ll have a repair manual this week to look into it more but it’s just strange that it instantly comes on at 21mph and instantly off at 20mph. I did determine it is NOT overheating or the overheating alarm. Until I can figure it out I’m running premix along with the oil injection (just like the breakin period) and not going more than a few hundred yards and start fishing with the trolling motor. Thanks for the reply.
HOW DID YOU DETERMINE IT WASNT AN OVERHEAT ALARM
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IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
update-I got a repair manual from one of our members who didn’t need it anymore-tested what I could, found nothing wrong, then began a methodical check and cleaning of all wires and connectors starting at the motor and working forward.Also replaced some switches on the dash that were corroded and in particular the panel on the bow for the trolling motor, live well, trim & tilt, and volt meter. Found several questionable corroded ground wires. Problem solved!