Small Block & Big Block Chevy Specific - Irratic water temp? Dropping under throttle why?

This may be a very stupid question but I couldn't find anything in the search. Weather has been cooler and i took the car for a drive last night. I noticed the water temp guage was kinda shaking a little bit for some reason, so i gave it gas to see what happens. the temp from ~185 to 150 when i went WOT. The more gas I gave it the lower the temp went instantly, even if i just revved it real quick.

What causes this? Is this a bad thing?

Perhaps the gauge is sensitive to vibration as it is probably a older unit?

Are you running a Thermostat? I dont see it as an issue unless the temp keeps climbing under cruise......

Resistance changes are volts/amps increase and decrease, otherwords I bet your alternator is causing the readings to vary.

Idk, it has never had a problem and then the other night started doing it.

Guage is pretty new, ~2 years.

Yes has a thermostat

Thanks guys, just wanted to make sure it is not a problem that I'll regret not fixing right away.

If it got hot then I'd be concerned, but cooler is fine. The T-stat may be stuck open, swap it out and see if the issue continues.....