Correct Temp sending unit location

[roan65]

I bought my first boat, a 2001 Rinker 192 BR. Originally it came with a 5.0 GM Merc Serial # 0M066428, but repowered to a 5.7 GM. I believe they used everything off of the 5.0 and swapped it to the 5.7.

My temp sending unit for the gauge is located on the starboard side of the thermostat housing. My gauge rarely reads anything for temp. I have grounded the tan wire and it maxes out the gauge, verifying that the gauge DOES work. I have added a ground wire to the sending unit, to verify that it has a good ground. I have replaced the sending unit as well.

I am a car guy, and it baffles me that the sending unit is on the freshwater (cold) side of the thermostat. I believe it never reads a temperature because it is reading cold water. Am I not understanding the system correctly? Shouldn't the sending unit be in the intake manifold where it would read the temperature of the water in the motor?

I have scoured the manuals and internet for pics or diagrams, and I don't see anything consistent. I've seen them in both locations, so which is right for my setup?

Any help is greatly appreciated, and I love the info that is shared on this site!

 

[Bt Doctur]

your most likely looking at the temp alarm, not the temp sender

 

[Fun Times]

First If you haven't yet, use an infrared temperature gun to verify the actual temp at the T/housing is reaching the 160+ degree mark......If the thermostat is stuck open due to debris, then the temp at the gauge reading will not go up very high if at all as the engine is running to cool.

The location of the sending units sound normal for stock applications.

Have you removed the T/Housing? Did you use a new base gasket between the intake and T/Housing? Did the gasket go on dry? Did the gasket have brass continuity rivets?

 

[wellcraft-classic210]

You can check resistance to gnd on the sensor with a dvm set to ohms and it should read a specific value for a specific temp.
-- cant seem to locate those values -- perhaps the experts can help

You also need to have a gauge compatible to that sensor value and a really good gnd on the sensor housing.