With the midget, there is a lightweight aluminum radiator with a water pump.
However, with the hydroplane situation, the cooling water is provided by a water pick-up below the waterline.
And as the speed and performance of these radically-different racing machines has improved, so have the engines that power them.
These engines have varied from stock four and six-cylinder automotive-type engines.
The V860 and Offenhauser The V860 remained competitive with midgets into the 1950s.