Buster, yes I was concerned about the heat, even though its not summer I have about 5 hours on it now, coming out of the engine the oil temp went up to about 210, and the head was a little over 325, 70 outside degress the other day , when I was fully loaded and WOT for 20 minutes, my side mounted oil cooler seems to be working ok the oil tank oil temp is about 50 less than coming out of the engine, I did alot of reading and best I can tell that most people watch there oil temp on harleys at the tank, this would be accurate if they do not have a oil cooler, and looking at other air cooled Aircraft in perticular, my flight manual says that when at normal flight oil temp should be 220 and 425 head temp, thats how you adjust your lean mixture in flight this is for a lycoming 260 hp O-540 CI. I don't know if this correct but I have found that the new engine(ultima) now has 30 percent more cooling fins on the new engines. The fans on the back automatically cycle at 180 oil temp and they do turn on and off during normal riding so far, I think they will stay on during hard running in the summer though. I may not be able to stay in the mud all day and dog it out but I can't do that in my airboat neither. I don't think it will stay a cool as a briggs so I will have to use alot of common sense.
Marty