Temp sensor issue

[JayBirdie88]

1988 Regal w/ Mercruiser, 175 hP, V6 #OB967952
I just installed new temp sensor, subtitute for #806490T. The needle on the temp gage goes over to the beginning of the red line for "H" and stays there while running. The engine is NOT running hot. After a cool down the needle retreats. I think the needle should level off at or near the mid point between "C" and "H". I have three questions: 1. Could I have the incorrect heat sensor? 2. Can the heat gage be calibrated to adjust the needle? 3. Is my thermostat incorrect? If the gage is calibrated for 140 degree but my thermostat is a 190 degree, that would cause a high temp reading? Interested in your thoughts?

 

[alldodge]

substitute for #806490T

What was the substitute?

Need an IR temp gun to find out what the temp of the thermostat housing.

Gauges are not adjustable. Check for 12V at the gauge and a good ground on the gauge

140 degree but my thermostat is a 190 degree

You have a 190 degree thermostat installed?

 

[muc]

If your engine is running at 190 degrees, it IS running hot.

 

[wellcraft-classic210]

Pretty sure you should be using 140 degree thermostat and that 190 is way to hot for a boat.

What was the original problem and when did it start // Why was the sensor changed

The gauge and sensor must be designed to work together & compatible to give the proper reading.

The sensor is a variable resistor that changes resistance with temperature allows a specific amount of electrical current to pass through it a given temperature -- The gauge should be matched to provide the proper reading at that temperature and current flow. The sensor housing must make a GND connection on its threads so using Teflon tape or other sealants can sometimes prevent that connection.
Sometimes resistance charts can be found and the resistance can than be measured for a given temperature with a multimeter.