Water temp gauge on 1979 29' Columbia/engine water

by Scotty B
(Ventura, CA)

My buddy has a 1979 29' Columbia sailboat, and the water temp gauge is still exceeding 180 degrees after running the motor for only about 5 minutes. Still not quite sure whether it's just the gauge or if the water is actually that hot. The thermostat has been replaced, as well as the exhaust, so not sure why the water seems to be reading so hot on the gauge. It's the original gauge which we're in the process of replacing but after testing it earlier I'm not so sure it's the gauge anymore. Please help. Thank you.