Temp gauge

[Southeast37]

Hello all,
Now that I have had some time to run my “new to me” boat Ive noticed that my
water temp gauge is not working properly. When I start my Ford Lehman 120 the temp will rise as the engine warms up like normal, settling at about 180. After some time goes by the gauge will shoot up past 200 and stay pegged like that for the rest of time the engine is running. Unless! I turn my ignition key off killing the power to my gauges and then the temp will “rest” and rise to that 180 mark and then once agin shoot to 200.
Now I know my engine isn’t overheating or running hot, Because I’ve replaced all the heat exchangers, plumbing and raw water impeller. Ive also checked with a IR gun and it’s sitting around 175-180 when it’s warmed up.

I’m aware of the obvious.. it could be the gauge or the sender it self but is there anything else any of you can think to check?
Thanks.

 

[C lectric]

THe wiring and ALL the connections must be clean and tight. Not just looked at and declared clean.

Even the crimps can be suspect.

When I first got my boat several guages were questionable and I fixed them by cleaning , retightening and reterminating those that still were operating improperly.

Some that were of squiffy condition, not outright corroded, but oxidized. I cleaned by using ROSIN paste and then heating it.
DO NOT USE ACID PASTE. THe rosin can remove oxidation enough to then present a good clean wire. After the rosin cleaning I used some alcohol and a tooth brush clean off the rosin. Just protect the area with paper towels. Then reterminate.

 

[Southeast37]

Thanks!
I went ahead and replaced some of the wires and went through and replaced on the plugs. Seems to be working for the moment but time will tell!