2002 Mercury 50HP 2-stroke continuous alarm

[Gulfsurfa]

I have a 2002 Mercury 50HP 2-stroke motor. About 4 months ago I received a continuous alarm, signaling high temperature. I replaced the t-stat and the alarm went away (been out 5-8 times since with no alarms). This past weekend I took the boat out (after sitting for 3 months) and the alarm went off again, continuously after about 15 seconds of bringing the boat on plane. I immediately slowed down, pulled into a canal and anchored for about 30-45 minutes. The tell tale, while running at slow speeds was not hot, and the lower unit was not hot at all. After, I turned the key over and the alarm was still on. I drove it about 1/4 mile to the ramp (idle speed) and it has since been stored in my garage, however, when turning over the key the alarm is still going off continuously. Obviously this can't be high temperature due to the motor being off for 3 days. Could this be a faulty sensor or horn?

I've changed the T-Stat after the 1st alarm (6/5/11)
I've changed the impeller when I purchased the boat (4/19/11)

Any ideas of places to check are very appreciated.

Thanks,
Jonathan

 

[CharlieB]

Re: 2002 Mercury 50HP 2-stroke continuous alarm

Unplug the temp sensor, turn the key on to see if the noise has quit due to a faulty sensor.

 

[Gulfsurfa]

Re: 2002 Mercury 50HP 2-stroke continuous alarm

It turned out to be the magnet on the floater in the oil reservoir broke loose and fell to the bottom of the oil tank signiling high temperatures regardless of how full the oil was. Unfortunately the only way to fix this is to replace the entire tank due to this only having a small opening enough to pour oil. I had to order and replace the tank. The alarm went away after doing so.

total cost: $139.17