Thermostat
The thremostat is in the water pump, outlet to the ride plate.
If your losing any anti-freeze, it may be your pressure cap. The cooling system on the 4-TEC is under about 14 pounds of pressure. If this cap looses it's ability to hold that pressure, you'll run hot.
I don't know if you have the ability to just replace the thermostat. It seems its an integral part of the coolant pump. You can find that pump under the heading in the parts index for "PTO cover and Magneto".........
If your getting an alarm, then it's also possible that your temp sensor is bad or shorted..............:cheers: