You can beat the hell out of most any automatic at road speed and the effect on the trans is negligible…it shouldn’t really heat much. Where things heat up are when the output shaft isn’t turning at all and there is some kW (HP or whatever) being applied to the input. Idle won’t do this but once you give it some gas, it takes very little time for the converter to get hot unless the vehicle is moving. Towing a heavy boat isn’t an issue at road speed…it makes no difference insofar as heat. I used to rebuild 3 or so E4OD’s each snowstorm we had…I got very good at it…I could get the trans and Xfer case out in < 15 minutes on a creeper from a F350 4x4…before the snow really started to melt of in earnest…hated that. Plowing is what caused the trouble. If you take a cold trans at say 20F and apply 1/2 throttle of say a 7.3 PS…within 3 minutes the torque converter heats to destruction (~300F). If you consider the physics, say 100 HP being disipated (dumped) at the converter is the equivalent of ~75,000 Watts. Or 750 100 watt bulbs. Now that’s more heat rejection than largest of coolers could contend with. Once one knows what’s going on (e.g. via a temperature guage on the outlet of the converter flow (exit cooling line))). one can make decisions such as stop plowing for a few seconds or the like. BTW, guages that read the oil pan oil temperature are so far removed from what’s important that if you ever read 300F there, your transmission would have been wrecked long ago.