Most OE thermostats will stay open when shot, where some aftermarkets will stay closed, much nicer to live with cooler temperatures than to have a head gasket blow or a plastic intake manifold melt. Be thankful your thermostat is staying open, though some aftermarket high priced thermostats do have a failsafe feature, and extra valve that pops open if the temperatures get too high. This is not a place to save a couple of bucks.
Like the guys said, check the thermostat housing temperature, if your hand has experience, good enough, big difference between 140 and 195. Not that I am paranoid, just experienced, like to put that new thermostat in a pot of boiling water with a cooking thermometer on the stove to know exactly at what temperature its cracking open at and indeed, it does open. Brand new out of the box always doesn't work and a lot of extra work to replace it if it doesn't. Ha, whatcha cooking dad? Thermostat soup.