didn't realize it had been going on for that long! You're a far more patient man than I.

Make sure the oil and water flow in opposite directions in the oil cooler. Opposite flow removes far more heat.

It is. Thanks.

What about running an external Oil cooler with electric fan, and duct the heat outside like a bilge vent
Summit Racing

or, FILL THE BILGE WITH ICE! It can serve double duty! LMFAO

What's your oil temp at cruise (3200rpm) and after a wot blast of say 1 minute?

Ok see if i understand you correctly. the oil in the pan is 270+ deg. oil exiting the cooler is 190 deg. right. so oil going thru your motor is 190 deg. so lowering the temp in the pan wont do anything for you cause its going to be cooled by the cooler before going back thru your motor.

If the oil in the pan is getting that hot, something is wrong no matter what the temp is coming out of the cooler. So what can be causing it to get that hot? Heat tranfer from the underside of the pistons is a big heat source. If you are running lean, your oil will get too hot for your oil cooler to handle. Same with any detonation. What's the compression ratio and what gas are you putting in it. Aluminum heads? Water temp? Are you flowing water freely out of the the engine, ie. (2) 1 inch dia. hoses? Too large of a prop possibly lugging the engine. How much timing are you running? Sorry for all the questions, just looking at the big picture.

190F - 200F at cruise. About 220F and steady at 4500. It is when I run at full throttle 5300 - 5800 rpm (depending on prop) that the crankcase oil starts a steady climb. 1 min WOT crank case temperature depends on how hot the crank case oil already is. Starting with hot oil it gets to about 240F +/-.

Any additional external oil cooler would have to be a second oil flow system separate from the main engine oil system since the oil flow rate would still be the same with the main system do to the bearing clearances and the current cooler is already cooling the oil that goes through it now to the thermostat setting of 190F regardless of how hot the oil is going into it.