Temp gauge question.

[ccustomrides]

I have a 1990 4.3 Mercruiser.
I dont know if my gauges are just getting old but here is what i got.

My temp gauge reads normal. I mean once warmed up it will read 150F and I even checked it with a heat gun.

Problem is when I turn the key off it wont reset. Before I would turn they key off and my temp gauge would slowly drop back to zero. Now it will read the same temp unless I restart the engine and it will read cooler temp or if I cycle the key from acc to off and it will drop the reading when its cooling down.
So is this normal or is there something wrong with wiring or gauge. I did take the wiring off for the temp sensor when I repalced the thermostat last spring.

 

[Alpheus]

Re: Temp gauge question.

Did the problem start immediately after you changed the thermostat?

What kind of gaskets did you use???

 

[Don S]

Re: Temp gauge question.

Is your temp sender in the intake manifold, or on the thermostat housing?
If on the housing, Make a jumper wire and hook it to the body of the temperature sender (NOT the wire terminal) and to a good ground and see if the gauge acts normal.
On the Mercruiser thermostat housing, the gasket has what they call a continuity rivet (soft brass) in the gasket so there is a good ground for the sender.

 

[ccustomrides]

Re: Temp gauge question.

yes it started right after replacing the old weathered thermostat.
I bought a kit on Ebay. It came with thermostat and gaskets. From what I remember it just came with regular gaskets nothing special. My sensor is mounted on the thermostat housing. I know that for sure. There is one wire on one side and two wires on the other side. So should I jump sensor body to ground? Also I noticed when it's super humid outside and I shut the boat off the gauge will peg the other way. It will read way high untill I turn the key on and then it's normal. Weird but I think thats just a old gauge acting up.