Hydros ride on a cushion of air; the boat contacts the water's surface on two sponsons (projections) and the propeller. The design is generally unrestricted, challenging those who wish to experiment in boat design and construction. Runabouts have certain restrictions, like minimum lengths. While there is great variety in runabout design, generally they have a flat riding surface, tapered to a point in front, and do not channel air under the hull. While, typically slower than Hydros, the thrills of racing runabouts are unmatched, just watch a runabout round a bouy and you’ll see the difference! Thirteen of the PRO classes are based primarily on motor displacement. They are sometimes referred to as “bore and stroke” classes. The maximum displacements of bore and stroke classes are 125cc (128.75cc), 175cc, 250cc (257.5cc), 350cc, 500cc, 700cc, and 1100cc (1133cc). There are no minimum weights in these classes, and in the hydro classes, there are few restrictions on hulls. The three largest hydro classes, 500ccH, 700ccH, and 1100ccH must utilize a reinforced cockpit (capsule) with the driver seated. The 125cc classes must use one cylinder motors. The 1100cc Runabout must carry two persons, a driver and a “rider”. Most bore and stroke classes utilize a fuel based on methanol and oil.
