The fast yacht Stiletto (length 95 feet, beam 11 feet, depth of hold 7 feet 9 inches; trial speed 23.7 miles per hour) was fitted with a 12-inch by 21-inch by 12-inch stroke Herreshoff pattern marine engine, operating at 450 revolutions per minute with steam supplied at 150 pounds per square inch by a Herreshoff coil boiler, and a propeller 4 feet in diameter, pitch 6 feet 6 inches, the Stiletto's exceptional speed was attributed to her lightness, powerful engine and fine lines; but the first two qualities were paramount.