Temp Gauge Too Hot

Engin starts and runs great. New 160 degree thermo. New impeller. No clogs anywhere, flow seems good. From cold start it takes about 7-10 min and a steady rising temp guage pegs at 250 degrees. Faster under load in the water. Removed the thermo and gauge stays all the way cool. Had a digital gun read outside engin temp about 30-35 degrees lower than gauge. What What What do I do. Could it be sensor, Gauge, Connections, Can I callabrate gauge with an ohm meter and if so waht is the spec. Its a faria gauge. 98 Moomba Outback, Engin is Indmar chev 350 5.7 / 310 hp. holly carb. I am so way over due for skiing this year. :( help ): Lisa

[Lisa +4]

98 moomba outback. Indmar 350 carb. Temp gauge bad??? digital heat gun says engin is 30-35 degrees cooler than gauge read out. have check so far; new impeller, no basic blockages, gauge ground acts up when lights turned on. Do I need a new gauge or sensor? Missing my nice weather skiing time. :( Lisa ):

[EUSTACE]

Do you have a raw water strainer? If you do I’ll assume you checked it.

If no: Disconnect raw water line right at the trans cooler, with a service mirror and a flashlight you will notice a fairly course screen, check it for debris.

At first blush it sounds like your temp gauge is working! Usually when they are not working they will either read nothing or peg as soon as you turn the switch.

As for the discrepancy of the heat gun reading, that is subject to the accuracy of the gun and the location of where you took the reading: a good spot to check is on top of the exhaust manifold prior to where the flex pipe begins.

Good luck, E

[superman]

Try this. Next time you run the boat take a long wire to run a new ground to check and see if it is your ground wire. I had this same problem with my gauge reading to high, turned out to be a bad ground wire. Let us know what you find.
________
maryjane (http://maryjanes.info)

[Lisa +4]

Thanks for the respomces. I am ordering a new gauge and hoping it will be here tomarrow. I will let ya know. :)

[zabooda]

You can remove the temperature sensor on the engine and put it in a hot bath of known temperature and see if the guage reads correctly. You need to know if the fault is with the sensor, guage or the wiring.

[Brian Raymond]

The ground wires for the gauges were daisy chained that year. I am not saying the gauge or sending unit is not at fault, but verify the gnd. wire is on the right hand post of the gauge when laying on your back, looking up at the backside of the gauges. Brian Raymond.