The C Racing Hydroplane (CracH) classes are based on the American-built factory racing outboard motors approved for use in the C Racing classes during the 1930s, ’40s, and ’50s. All approved motors feature 2-cylinder engines with 30 cubic inches of displacement. The C Racing Hydro class has a maximum propeller height limit of 2.25 inches. Propeller height is defined as the maximum distance that the propeller blade may extend above the bottom of the boat.(measured from the true bottom—not measured from any tunnel).