the temperature will go up a bit after you shut it off because the water is no longer circulating, but is still absorbing the heat from the engine metal, sounds like the gauge may be OK .... the best check is to use a digital laser thermometer, check the temp of the stat housing when it's up to temp, don't depend on a dash gauge [and it's sender] until you check it in action on the vehicle .... a 283 works best with a 180 stat, they like running 180-200
Bill
