Temp gauge

Ok, so I got my boat running last week, after replacing the fuel pump. Now the temp gauge doesn't seem to be working. After it idles for a while, the needle starts to move, and then it drops down to the bottom. If I turn the motor off, and then start it back up, the needle will go to the middle (180??) for a sec, and then drop back to the bottom.

My question is: Is this a problem with the water temp sensor, or water temp sender? How can I trouble shoot? If I hook a multimeter to the gauge in the back, if there is no current coming through the wire, can I assume it is the sender?

Thanks,

Robb

Are you running the boat on the trailer?

Do you have a flow of water going through the engine?

I have seen similar symptoms when there was no water for the sensor to sense.

Otherwise, I would guess that it is either the sensor or the wiring. The sensors generally are not expensive or hard to change so that would be my first attempt.

The temp sender will be a single wire sensor, mounted in the water jacket, probably near the thermostat on top of the intake. Ground the wire to the engine, with the key on, and see where the guage goes. It should peg the guage. If so replace the sending unit, but that is assuming the guage is malfunctioning when you being the test. There may be an "intermittant problem" (<scary words LOL) with power or ground to the guage.

I am running the boat on the trailer. Yes, I have flow of water through the motor, it is coming out the exaust.

(Message edited by boarder_x on April 08, 2006)

Does the h2o exiting the exhaust feel luke warm? If not could be stuck open thermostat or just that the hose is supplying cold water at pressure thus the boat cannot "warm" the water lots more pressure in a public water system than a lake.

I had a problem like that on my boat. Turned out to be the ground wire. Next time out take a wire hold it on the battery ground and to the ground on the gauge. Will take 2 people to do.