Are you using a direct-reading gauge, or an electric one? The direct gauge will have a very thin tube surrounded by a spring-looking shield that bolts into an adapter on the side of one of the cylinder heads. The electric gauge will have a wire going to the sending unit somewhere on the engine, either the cylinder head location, or one near the thermostat housing. You can test the direct gauge by putting the sender bulb into a pan of boiling water. It should read 200 degrees or a bit more. If you ground the wire from the electric gauge to the sending unit, the gauge should go to a full hot indication.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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