My 773 has always been slow to warm up and after draining the coolant to replace a valve I can only get it to take about half the coolant that came out. I assume the thermostat isn't opening. I don't work it very hard but I think it should warm up completely. The gauge barely gets to the normal range. Is this normal? Bad thermostat? If I just start it and let it run at around 1/4 throttle, how long should it take for the temp gauge to reach the middle of the normal range?