That race was won by Dorothy Levitt, driving an 11-meter (35 ft) boat, powered by a 56-kilowatt (75 hp) Napier engine, at an average speed of 31.4 km/h (19.5 mph).

[1] One reason for the rule change was to end the domination of its star driver, Gar Wood, who had won five consecutive Gold Cups from 1917.

"King Gar" had entered fifteen Gold Cup heats during those pinnacle years.

[1] In 1929, the 725 cu in (11.88 L) Class was introduced by the Mississippi Valley Power Boat Association (MVPBA).

These boats were popular in the Southern and Midwestern US, but did not attract the media attention that the expensive and exotic-looking Gold Cup Class counterparts had.

[7][8][9] The next entrant with turbine power was the Pay 'n Pak in 1980 on the Columbia River at Tri-Cities,[9] but it flipped 2½ times in a test run prior to the Sunday heats.

They were called "Unlimited" because they were the only class of boat racing the APBA that had no restrictions on the displacement size of their piston engines.

Almost all the H1 Unlimited hydroplanes are powered by Lycoming T55 turbine engines,[18] originally used in Chinook helicopters.