Merc 5.7 Temp Gauge Sending Unit

[MelLandry]

1977 Slickcraft. Mercruiser/Chevy 5.7 carborated.

I was cruising home yesterday and the engine started to sputter. I opened the engine cover and there was water in the bilge slightly over the top edge of the oil pan. (We had experience a hard rain and the float on the bilge pump did not function as designed). I turned on the bilge manually, pumped out the water, and the boat ran fine for the next quarter mile to the closest ramp (where I had someone come pick me up). It was running hotter than normal in that quarter mile... around 175 (normally around 125).

I brought the boat home, replaces all the fluids, changed all filters, and she fired up fine, and ran fine. I could place my hand on the riser, and under the water coming from the outdrive (temp check).

BUT... the temperature gauge is pegged out at the max. It is like that every time I turn the key on (even with the engine off). Hours after the engine was turned off and was room temperature, the gauge is pegged out when the key is on.

So TWO questions:

1) Is their anything else I should do to the engine to ensure I don't cause any futher damage.

2) Can you help me troubleshot the temp guage. (test proceedures, location of sender on block... etc)

 

[Dakota47]

Re: Deep Water In Bilge

Re: Deep Water In Bilge

sounds like you need a new tempature sending unit. check the gauge too.

 

[MelLandry]

Re: Deep Water In Bilge

Re: Deep Water In Bilge

Thanks man.

I found the sending unit. When I tried to unscrew the nut that held the wire to the top, it just spun with the wire and didn't loosen. Any secrets to getting this thing out.

 

[Reel Poor]

Re: Merc 5.7 Temp Gauge Sending Unit

Cut the end of the wire off at the sender, replace the sender and the wire end. With the wire disconnected turn the key on, if the gauge still pegs the gauge is faulty or the wire is shorted to ground somewhere.