temperature sending unit

[tonytav]

I bought a boat this year and it is in the water. The temperature gauge does not work. I took the wire off the sending unit and grounded it out. The needle on the guage moved. So-I assume the gauge and wiring work. I figure it is either the sending unit or the thermostat is stuck in the open position. I was going to start by changing the unit. Can this be done while the boat is in the water? Should I get one from the marina for a Mercruiser 5.7 or will one from the auto parts store work? If I replace the unit and it still does not work, can I use it for the season with the thermostat stuck open? The boat has a temperature alarm. Can I test that by jumping the two wires together? Can I periodically check with an infrared thermostat? Thanks for any help. Tony

 

[poormonkey]

I had a similar issue and it turned out the part of the housing the sender unit was in, wasn't making a good ground via the housing the part it bolts down into. So, I had to use a wire brush after I took the top thermostat housing off, and brush that piece and the part where it connects to with the motor. After that, I got my temperature sender working again.

You should have no problem changing your thermostat while your boat sits in the water.

As far as using a regular automotive thermostat or a marine one. I would recommend going with a marine thermostat.

As far as jumping the wires together, I wouldn't do it if it was me. I would check to make sure the upper housing is making a good ground to the part of the motor it bolts up to. If that doesn't fix it, I would then replace the sender unit.

 

[poormonkey]

sorry double posted