I couldn't get a 16mm bushing for the Sunpro gauge I got, so I took it back and ordered one of the more expensive ones from Hoye. I installed it this morning, filled the system with pure water, and started to do some testing.
Just running the tractor once around in a little circle in front of the house brought it up to about 190. About four times around a small field with the bush hog brought it up to about 230. At that point I quit. I notice that the top hose of the radiator is very hot to the touch and that the bottom hose is almost cold. Top of radiator is very hot; bottom is cold.
Aaron at Hoye says they mow just fine with a similar size cutter in 90+ weather and without a water pump, and that the temp hangs around 190.
I've done all the cleaning tricks, and flushing tricks I can and it's still running hot. So the next step (about the only think left short of a water pump) is to get the radiator to a shop and see what they can do or say about it.
