Water temp sender unit on 1988 37lx 180hp

"I installed new dash and Fari

"I installed new dash and Faria gauges on my boat and have had pretty good luck so far with most of the gauges except the water temp. gauge. I rebuilt motor last winter and only have about 25-30 hours on engine so far. The gauge has been wired correctly and looks like it wants to work when I key up but it only goes to around 125 after around 30 minutes running time. (warm up)
Question: Assuming that the sending unit is good! Could there be compatibility issues with the original 470 sending unit and the Faria marine gauge that I have correctly wired up? Also, I did not remove sending unit in the rebuild! Could there be alot of corrosion on the coolant side of sender causing it to give a weak signal? As I said the gauge moves slightly but I know the engine has to be hotter than 125F and I put my hand on the manifold and it was fairly hot but I was able to hold my hand on it for awhile. I believe that the motor reached operating temp. How do I test? Thanks, Tom"

"[b]"I put my hand on the

""I put my hand on the manifold and it was fairly hot but I was able to hold my hand on it for awhile. I believe that the motor reached operating temp."

Ayuh,... If you Can hold your hand on it,...
The gauge is probably Right...
Depending on which T-Stat you used, I rather doubt you can hold your hand on 180° for more than a Second...
Ditto at 160°,... Maybe at 140°, but that's questionable..."

Bondo is right. To test the g

Bondo is right. To test the gauge just gound the sender wire. It should peg the needle. If not then you have a wiring problem; suspect corroded internally sender wire. You can pull the sensor and clean the copper end and reinstall. You need a 160 F. T'stat.

"Thomas McGee
Beg Borrow or S

"Thomas McGee
Beg Borrow or Steal an infrared thermometer, and test the engine heat against the gauge reading.
Bert"

"Bert, you were reading my min

"Bert, you were reading my mind! Thanks for the support. I will test gauge first, then remove sender which I was dreading, then do engine test with gauge and then see if a mechanic buddy has an infrared thermometer. thanks, Tom"