re: Towing a boat with 1/2 ton truck.

I would posit it would be fine every day of the year for a short trip but anything more than about 10 or so miles you are going to cause the transmission to run hotter than designed and it is going to fail prematurely as a result even with regular fluid changes. Even on flat highways there are hills and heat builds up....and heat crystalizes hydraulic fluid which exacerbates the heating issue which in turn exacerbates the crystallization. The engine temp is not the issue....the transmission is cooled by the same radiator but the water exchange is such that the volume will make the engine temp appear slightly higher than normal while the transmission temp is significantly higher than normal. As the issue gets worse it will cause the engine temp to rise also but by the time it shows up on the temp gauge its usually too late for the transmission. Transmissions are cheaper than trucks though.....