Help... 75hp Mercury 2 stroke alarm keeps going off

[Ponyboy1995]

I have a 1994 Bass Tracker with a 75hp mercury 2 stroke. Took it out last weekend & it ran great. Out for several hours fishing. On the way back in to the dock I ran her hard & fast trying to use some old fuel. When I slowed down to idle a constant beeping alarm came on so I shut it down. After about 5 min or so of trying to figure it out I started it back up & after a minute or so I came back on. This week I changed out the thermostat & the impeller. I started it last night & after about a min or 2 the alarm started going off again. The stream coming from the pee hole was not hot & the engine was not hot to the touch. I am at a loss. The only other thing I did recently was change the plugs. It calls for NGK but the shop said they no longer make that plug & gave me autolite plugs. I don't think plugs would cause an overheat alarm but I could be wrong. What should i do next? I am at a loss.

[EuropeanAM]

The shop lied. Get those Car-Plugs out of your marine engine now... and go get a set of the correct NGK Spark Plugs.

Be glad to verify that plug number for you if you provide your engine's serial number (Likely BUHW-2).

Once you have the correct plugs in it, see if the alarm continues. If it does, try disconnecting one of the blue wires on the engine-mounted oil tank, and then test to see if the problem remains (this is done for testing purposes ONLY).