As I understand it, only a small percentage of heat is given off at the motor end (5%). What you described should make very little difference to the total amount of heat being put into the water. Maybe 1% at best. This would be nowhere near enough to compensate for the different wattages between the little giant and the two smaller pumps. It's because of the saltwater enviroment that the pump was designed for that the propeller was as you described . Heat had nothing to do with it.
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