Mercruiser 3.0 in regal 1800 - Temp gauge problem

[jon middleton]

The gauge on the boat is reading 190f I have changed the the sender unit, thermostat, exhaust manifold and recently done the head gasket and changed the temperature gauge itself and it still says the engine is overheating. When using a IR thermometer next to the sender unit is says the engine is 160f . is there something in the wiring loom giving the false reading??

Any help would be great !!

thanks
Jon

 

[Bondo]

Re: Mercruiser 3.0 in regal 1800 - Temp gauge problem

I have changed the the sender unit, thermostat, exhaust manifold and recently done the head gasket and changed the temperature gauge itself

Ayuh,... What about the Impeller,..??

 

[jon middleton]

Re: Mercruiser 3.0 in regal 1800 - Temp gauge problem

yep I changed that as well ! is there an iline resistor in the wire from the sender to the gauge?

 

[tschmidty]

Re: Mercruiser 3.0 in regal 1800 - Temp gauge problem

The temp gauge is based on resistance. So get an ohmeter, check the resistance at the sending unit (between the terminal and ground) and then check that same resistance at the gauge. My guess is a bad ground somewhere at the gauge side of things.

 

[Silvertip]

Re: Mercruiser 3.0 in regal 1800 - Temp gauge problem

When measuring sender resistance the sender wire must be disconnected. An incorrect sender will cause an erroneous gauge reading. The gauge and the sender must be compatable. There is no resistor in the sender wire between the sender and gauge. If ground was missing the gauge would not work.