Not sure where the red green line is,,,mine runs about 170 to 180 degrees f,,[if I remember right],,when working out in about that temp,[hardly ever work it when its that hot,,,although its been in the 90's here in wva,,for past 4-5 days now..
I would first make sure its got plenty of coolant and you don't want to rich a mix,[more than about a 50 -50,,, 60 - 40 mix,antifreeze/water],,than I would get one of those long airguns and blow raditiator out good with air compressor,,starting from back,,and look at raditiator openings and make sure you can see through it,,air has got to pass through raditiator,,,,,,than you could check your fan and belt and make sure all that stuff is working good,,,,one other thought,,,mine [a 254] doesn't have a tach,,,so I got to go by sound and feel when brushoging or tilling,,,have learned that you don't need to give it more than about 3/4 throttle to cut and till,,,,more rpm's you are running,,more heat you are making,,,,,course if you need it,,crank it up,,but alot of the time when I'm mowing,,,don't have it much more than 1/2 throttle,,,,just a thought there,,,,thingy