Temperature Gauge reading

[Muscats]

Hi everyone,
we finally got our 2007 2100 SC3 on the water for a couple of weeks, however, I was getting some strange temp readings. The gauge would sit on the cold side for several minutes after starting the engine then would move up to just under 175 and then drop all the way back down after about a minute. This would happen a couple of time while we moved through the 4 knots limited area, probably around a 10 minute trip. I noticed the tone of the engine change when the gauge moved up and I assume that the thermostat must be open when the reading goes up.
Is it normal for it to drop back down so quickly and to only get a temp reading when the thermostat is open?

Water temp was around 65 degrees

It seems to give a normal reading when cruising at high speed.

On a separate issue, anyone know where I can get replacement switches for the dash, in particular the On/Off/On switch for the nav lights and make and part number they would be. I am in Australia, but happy to order from the states or anywhere really.

Paul

[mmwjr]

Paul welcome aboard.

It is not normal for the temp to change like this, once warm it should stay that way. I would use a handheld IR temp sensor to verify the engine temps at the t-stat housing, manifolds, and elbows.

May be time to replace the t-stat which will also replace it's gasket. This gasket has brass eyelets in it to provide ground for the temp sensor, over time these wear away and the ground circuit gets flakey

[cdhunter]

Paul - Can you post a picture of the nav light switch you want to replace?

[tomkwsnc]

We installed new switch covers with labels from New Wire Marine - fast shipping and good pricing.....

https://newwiremarine.com/