Thanks for all the replies.
For those that had questions:
Runs slightly into the red line during the hot summer months only, and only after 2 hours or so of mowing. all other times runs fine.
I can take off the cowling and everything cools down to below the red line.
I mow FULL throttle. High or low gear doesn't seem to change it much...neither does dull or sharp blades.
No bent fins, no engine issues that I can find, clean radiator. Already replaced thermostat once. Have been reluctant to run without one, but may do so to help water flow.
I am really wondering what it would take to add a better quality temperature gauge? With those reporting their BX always stays in the middle, I am wondering if they changed something? I am also wondering if it would be worthwhile to change the temp sender?
I would get one of those IR guns (someone else already mention this)that you point and shoot and hit the radiator and the engine block and compare to your guauge. I would even try pulling the dipstick and shoot it (if you can, maybe surface area too small). If the guage is off, take a sharpy and mark the area on the guage that is safe and not worry about it.
You could spend too much time and money for something like an idiot guage anyways. (Don't anyone take offense, I only call them that because they are typically unreliable in farm equipment).
If the tractor is over heating your overflow tank would be blowing excess coolant all over the place.
I've ran my tractor in 95+ heat and notice the temp guage rise a little bit because of it, but never redline and I cut for hours in this heat.
Other things to consider for the safety of your engine, is run a slightly high vecosity oil (which from the sounds of it wouldn't hurt if the temps are that high normally.)
SOmething else to look at is your lines running to and from the radiator, check them for soft spots, possibly could be collasping under the extreme heat or maybe there is a kink. Many people have rna into similar issues with those lines.
And Probably the messiest thing to do is drain the system run some water through it, diconnect the line feeding the radiator and check the coolant flow from the pump to the radiator, I don't know what a desired flow rate or pressure should be, but that could point to another issue.
But the IR gun would be your best bet to get an idea if it is just your guage.
I don't think an oil cooler would help that much, maybe but I think it would only bandaid fix the problem if there is one and not really correct the real issue that could get worse.
If you really think the heat is hurting the mower, send off an oil sample periodically to a place and let them test it. The tests would show if the ooil is overly used.
Before I wear out this topic, have you driven the tractor into the shade once it started heating up? I know it is funny, but I know when out in the fields, the fields seem so much hotter and I wonder if the ambient temperature around it could be affecting the sensor or actually warming up the tractor. Maybe this one is out there, but when I used to ride my air cooled motorcycle, when I got out of the city, the temp on it would actually go down because it wasn't as warm in the country from the radiating heat from the pavement. Again, don't give me too much crap for this one, it was a just thought and maybe not a real good one.