A hydrofoil stabilizer is a device attached to an outboard or inboard/outboard boat motor to aid the boat in coming up on plane or leveling out. The boat is also aided in remaining on plane at slower speeds through the use of a hydrofoil stabilizer. Acting much like an airplane wing, the stabilizer lifts the stern of the boat as it travels through the water, pushing the motor up and out of the water, resulting in the boat coming up on plane in a much shorter distance than a non-hydrofoil stabilizer-equipped boat. Beyond a performance aid, the stabilizer is also a safety item and improves the driver's vision by allowing the boat to operate with the bow in a lower position, thereby aiding in the operator's vision over the bow of the vessel.
As a boat travels through the water at slow speed, the bow typically rides high in the air with the stern very low in the water. This causes the boat to use a great deal of fuel, as it is pushing a large flat area of the hull through the water. As the motor speed increases, the stern is pushed up and the boat begins to flatten or plane out. The hydrofoil stabilizer helps bring the rear of the boat up and shorten the time it takes to get the boat on plane. Once on plane, the boat glides much more easily through the water and is much easier to maneuver by most people.
For many boats, the ability to remain on plane at slow speeds is greatly enhanced by the addition of a hydrofoil stabilizer on the motor's lower unit. Commonly bolted to the motor's cavitation plate, the hydrofoil stabilizer does not affect the maneuverability of the outboard and does not reduce the fuel economy of most engines. The hydrofoil stabilizer actually improves the fuel economy of most boats due to the boat coming on plane easier and remaining on plane at slower speeds. The typical stabilizer is installed in a matter of minutes by most boat owners using only small hand tools.
On many outboard-equipped boats, the boat suffers from a series of rising and diving actions called porpoising. This is often caused by the use of an outboard motor that is on the verge of being too small to adequately power the boat to plane. By installing a hydrofoil stabilizer, the boat will often come on plane without the rise and fall characteristics associated with a small motor.