95' Mercury 115 temp alarm

[Jerry Young]

I have a used motor and do not know the history of the motor. The temp alarm came on. I took off the cover and placed my hand all over the engine to feel for heat. There were no hot spots and the engine was just barely warm to the touch, but the alarm stayed on. After an hour, I cranked back up and the alarm was on immediately. The SELOC manual says that for the Mercury 70-115 HP motors that the temp switch is closed during normal operations and opens when hot. All the other HP motors operate just the opposite. Is this a misprint or wrong information, because my sensor operates as an open circuit when cold and short when hot. Has someone installed the wrong sensor? What is the correct part number for a 95' Mercury 115 HP motor? Can you run the motor without the thermostat and poppet valve?

 

[Jerry Young]

Update: I tested the temp sensor and it is open when cold, shorts when hot, and resets when it cools off. Reinstalled and without cranking motor for over 24 hours (completely cold motor), key turned on, I am getting an intermittent horn that is weak and scratchy. When I jumper the blue/tan wire to ground (simulating a hot motor) the horn is sharp, clear, and loud. With the temp sensor not connected and connecting only the blue/tan wire from the oil warning module to the blue/tan wire of the wiring harness to the remote control (horn) I get the weak, scratchy horn. The wiring harness to ground reads open. The oil warning module to ground reads 12 ohms. How do you test the oil warning module?

 

[sam am I]

http://forums.iboats.com/forum/engi...erheat-temp-sensor-and-temp-gage-sending-unit

 

[joed]

It is very common for the oil sensing module to go bad on those years of engines. You can connect the temp sensor direct to the wire from the harness and bypass the oil module until you get a replacement module. This will give a temp monitoring but you will need to manually monitor the oil levels.