My 2000 tohatsu 40hp md the oil light on the tach came on today, has not done this before. I was leaving when this happen but once getting to the dock and again when loading up. It has auto oiling but the tank is all most full. Don't think it was running hot because if was fishing in a marina so it was not ran that long. Done some reading couldn't find anything that i thought the reason.
I did read that the oil filter and gas filter should be cleaned and replaced and that has not be done in the five years i have had it.
I would start by changing/ cleaning the filters. I would also find the sensor and check to make sure you have a good connection from wire to sensor and no broken wire.
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Charlie Weaver USN/ENC 1965-1979