Has it always run up there at 200? If not, start with the obvious, like strainers, impeller, and heat exchanger service. In my opinion, 99% of the time it is not the thermostat. Your manual (if you have one ) should tell you the acceptable temp range. Good luck, hopefully an easy fix.
Are you heat exchanged?I had a couple 300's,heat exchanged,they ran 195 when being run 2200.When the exchanger needed to be cleaned hey would go 200 ,or a little higher.I think the heat exchanger is border line big enough for this model.I put over 15,000 hours on this way.The hot tank sure gets good and hot.
6076 is the 300.Its not a big deal to remove the core and clean it.Drain the coolant down and remove the end caps and the core slides out the port side.Most of the time the o rings can be reused,but its a good idea ti have a new set handy.Does the engine turn 2400 wide open? If you are over wheeled the temp will climb also.