helllp with cooling issue

The results of tonights tests. It is a 180* thermostat. According to my IR thermometer, it started to open at about 195* and was fully open at 205*. It stayed open until the water had cooled down to about 175*. As a check, the IR read 215* when the water began boiling, not a rolling boil, but bubbling to the top.
I repeated the test 3 times with the same approx. numbers each time.
I guess my question now is, should the thermostat start to open at 180, or be fully open at 180? I plan to pick up a new one tomorrow and will test it prior to installation.

As to the flatness of the housing and intake, they both checked out flat. I used a disc of self stick 180 grit sandpaper on a sheet of glass to check the housing, then stuck the paper to the housing and checked the intake. I think I will get the O ring housing and hope it works.
C