D4 7U water temp

How far up in the green should the engine run?

needle approx middle to 3/4 in green is 165 to 180 degrees on cat gauges, they can differ a bit from gauge
to gauge. i have determined this by warming up water in a pot on the stove with a hand held radiator thermometer and gauge sending unit together in pot to test gauge and get an idea of the range before installing new gauge on tractors. i also do this with new thermostats before installing to make sure they open when there supposed to.if your your radiator and cooling system is clean and in good shape you may need to cover the radiator screen a bit with a canvas to get water temp up in cold weather.