My older 330hp 454 wont reach the proper operating temp. Gauge barely moves off 110 degrees even after a 5-minute wide-open run. It is not the gauge, have replaced and checked both the gauge and sending unit. If I ground the gauge wire out, it maxes out the gauge. The thermostat, sleeve and gaskets have all been replaced. Still running the circulator pump, with bypass from pump to intake manifold. Ever since I bought the boat it has been this way. Is there something I am missing?

Just a thought, are you using the bottom t-stat gasket with the grounding tabs in it? after running the engine have you taken a grounding wire of sorts and touched the sending unit body and a good known ground to see if the gauge works? Also did you have this problem before you changed the t-stat or after?

John S.

The only other reason I've seen for a cold running engine was that all cylinder were not firing.
Gary

It has always done it. That is why I changed thermostats.
When I took it apart it did not have the grounding gasket.
I did put one on though (I wondered what those tabs were for).
Maybe I used too much gasket sealer? Now that I know what those tabs are for I will make sure they are clean.
I will let you know what I find.
Thanks.

A few years ago I solve a problem like yours. Depending on what thermostat house you have it might be possible to install the thermostat wrong. It must be in the middle of the T-house, not in the top. Otherwise the water flows right thru the engine.

Another thing: are you sure the sender are the matched for your gauge.?

All right, the thermostat is new and installed correctly, the sender is new, the gauge is new, both auto meter. I am using the gasket with the grounding tabs and still the damn thing barely comes off 100 degrees. If I install a jumper from the sensor to the intake manifold it pegs the gauge like it should.
Now I am wondering if the sender is in the right place? If your looking at the engine from the front. It is on the left side of the T-stat housing. Is this right? By the way the engine runs great I just want to get the gauge working properly so if there is a problem in the future I will know about it before it is to late. Any ideas are truly appreciated.

Okay, then try to place another sender in your intake manifold. There should be ½" thread just beside your T-house. This is the thrue water temp from the engine. I start thinking about you maby have a corroded T- house. Small holes inside the T-house could lead he cold seawater direct to sender

Had the exact problem last year. New gauges,wiring etc. Found that I could not use a parts house sending unit on the gaffrig gauges. Purchased gaffrig sending units and cured problem on both engines.