One of the cheapest ways to check the operating temperature of your engine is to pick up a couple of those temperature sensitive test crayons. You simply get crayons in the temperature range your engine and thermostat should be running and mark a few lines on the thermostat housing. When the temperature range of the maker is reached the mark will change color to let you know that temperature has been reached.
If the engine is supposed to operate at 195 degree, a 195 marker crayon will change color when it reaches 195 degrees. If it does not change color after sufficient warm up time, then you have a thermostat that is stuck open, or not the right thermostat.
If you get several markers in the 180, 185, and 190 degree range, you can tell if it's the wrong thermostat, or just stuck, before you have to start unbolting things. Sometimes people install a lower temperature thermostat, or simply remove the thermostat thinking that a cooler running engine is better?
....Rich
...Rich