So I was able to touch the exhaust with my hand without burning or anything (didn't feel too hot), thought about maybe the sending unit going out however there was definitely a perceived loss of power or "limp mode"?. By sending unit are you referring to the temp sensor in the top of the block near the thermostat? If that sending unit was going bad could it cause the boat to run with less power ("limp mode") to protect itself thinking it was overheated even though the running temp was actually ok?

Also I'm about 6'1" 185-190lbs, I don't think the added stress of towing me could have pushed the boat over the edge to overheat right? I would guess that 5.7L V8 could barely tell I was back there?