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Mercury 40hp classic 2 stroke temperature sensor or stator?

G

G&G

New member
I have a 1997 mercury 40hp 4 cylinder classic 2 stroke outboard engine. Had the boat out today, alarm was sounding, disconnected the oiler wires and alarm continued. ( I have premix in the fuel tank) I pulled the hood and the checked to see if the engine was hot but it was not. I could keep my hand on the engine. I could not reach rpm’s over 3k with a top speed of 7mph. The tach was intermittent and the volt gauge creeped up to 14 volts. I was leaning towards stator, but after taking to another person they suggested checking the temp sensor, that the engine may be in limp mode. I removed the sensor and had continuity at room temperature. I went ahead and dunked it in boiling water and again I had continuity. Marine Engine shows I need part number 87-16775a3 which of course is expensive. Can I use 87-16775a1 or a2 instead? It appears the only difference is the terminal connection.
Also, am I on the right path or am I misdiagnosing this thing?
Thanks for any advice.
 
Solution found, it was the temp sensor putting the engine in limp mode, I feel a little better spending the extra cash on the right part now.
 
That engine does not have a limp mode. It has the old style switchbox design ignition system. Something else is root cause. That tan wire sensor just closes to ground and sets the horn to sound in the control box to alert you of a cooling issue. Check your waterpump impeller.
 
Thank you for your reply, the engine is not getting hot. It would not throttle over 3k rpms until I unplugged the temp sensor, then it ran as it should. Is there anything else connected to the temp system that may be the culprit.
 
So you disconnected the tan wire coming out of water jacket cover and the engine ran better? That temp sensor has nothing to do with running quality other than alerting you. Strange for sure..
 
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