Like any boat, a hydrofoil needs a propulsion system to move. For hydrofoil vessels, electric propulsion is an excellent choice. Electric motors deliver high peak power and efficiency, which fits perfectly with the physics of hydrofoils. Also, the low energy consumption of hydrofoil boats makes sustainable propulsion much more affordable.

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Different propulsion systems

There are three main propulsion options for hydrofoil boats, each with its own advantages and trade-offs:

1. In-Hull Motor with Driveshaft

In this setup, the electric motor is housed inside the hull. Its power is transmitted to a propeller through a driveshaft that passes through a vertical strut. A gearbox is usually required to match the motor’s high rotational speed with the propeller’s optimal speed.
Pros: Robust design, motor protected inside the hull
Cons: Gearbox adds complexity and weight

2. In-Hull Motor with Waterjet

Here, the motor is also inside the hull but drives a waterjet pump instead of a propeller. The pump sucks in water and ejects it at high speed, producing thrust.
Pros: Mechanically simpler, no gearbox or long driveshaft needed, less risk of debris ingestion.
Cons: Often less efficient than a well-designed propeller due to energy losses in the pump

3. Underwater Pod with Direct-Drive Motor

In this configuration, the motor is located in an underwater pod, directly driving the propeller without a gearbox (see image).
Pros: Higher efficiency (no gearbox or driveshaft)
Cons: Increases drag, harder to maintain, requires careful waterproofing of motor and electrical connections

Choosing the Right System

The best propulsion option depends on the vessel’s mission, design, and operating conditions. Each system has advantages and trade-offs, and selecting the right one is key to maximizing efficiency, reliability, and performance.

At Flying Fish, we combine our expertise in hydrofoil design and green propulsion technologies to help clients choose the best solution for their vessels.

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