How Hydroplanes Work

Gear Box

The gear box sits in front of the turbine engine. An input shaft running from the engine to the gearbox turns the gears inside. Then an output shaft from the gearbox spins the propeller allowing the boat to move forward. An unlimited hydroplane gearbox reduces the engine RPM roughly in half.

Long Shaft

The long shaft is inserted in to the gearbox and connects to the short shaft to spin the propeller.


Between the long shaft and the short shaft the coupler joins the two together.

Short Shaft

The propeller is attached to the short shaft. When teams make a propeller change, they remove the short shaft at the coupler and replace both shaft and prop.


The strut holds the short shaft in place at the rear of the boat. Adjusting the strut's angle allows teams the ability to either raise or lower the boat's nose. This change can not be made during a race weekend as it requires dismounting the strut and setting the angle in the shop.

Stuffing Box

The long shaft that comes from the gear box has to exit the boat at the same angle as the strut's setting. This prevents binding while the shaft spins. We cut a hole in the boat's bottom to accommodate the long shaft. The stuffing box holds the long shaft in place as it "pokes" through the bottom of the boat.


The shoes are the weird looking "bumps" in the back of the boat, under the waterline and directly below the fairings. The theory behind the shoes is that it hydrodynamically helps support the boat.


Runners are the actual running surface on the boat's forward underside. The team can adjust the runners while the boat is on the trailer. Adjusting the runners can dramatically change the boat ride. The anhedral and Dihedral angles also can be adjusted to change the boat's racing attitude.


The T55 Lycoming L7 turbine engine was originally created for the Chinook helicopters (you often see a Chinook at Seafair for the national anthem or during the airshow. If you live in Seattle you see them regularly just flying through the airspace). The turbine engine produces about 3,000 horsepower and can move the boat at right around 200 mph in a straightaway such as San Diego. This engine runs on virtually anything. It was designed so that if the soldiers flying these helicopters ever needed to gather fuel to fly the helicopter, they could use whatever combustible they could find to pour in it and get them out of danger.