In brief: 2,000 W · waterproof wireless remote with telemetry · magnetic kill switch · active water-cooling · ESP32 · built for under €2,000 (vs over €10,000 for commercial models)
Some leisure gear is so expensive that you never actually buy it. Electric jetboards are often in that category. So I decided to build one myself, integrating everything that makes a real electric watercraft: propulsion, battery, safety, cooling, wireless control and energy monitoring.
The prototype puts out around 2,000 W: enough to carry two people on the board and tow others on tubes attached at the back. Runtime: about 3 h per battery.
I built in a magnetic kill switch, like the ones on professional jetboards — something many maker projects skip but that I consider essential, because a machine with this much power can take off very fast with no one on board. The kill switch immediately stops propulsion if the rider falls off.
The ESC (180 A max) drives a motor rated for ~50 A, with a comfortable margin, on a battery that can go up to 80 V.
The ESC is water-cooled: a pump kicks in as soon as the temperature rises, drawing fresh water from above the motor, discharging at the rear of the housing, with an easy-to-clean mini-filter to keep algae out of the pump. All of this in a hostile environment: moisture, sun, impacts, vibration, high sustained power.
An onboard ESP32 receives commands from the waterproof remote, the kill-switch state and the measurements (voltage, temperature), drives the ESC within the motor's limits, and sends telemetry back to the remote. A display on the housing tracks the battery level — so you never end up out of power in the middle of a lake.
Handling high power in an aquatic environment · protecting the rider in case of a fall · preventing overheating and electronics failure despite variations and heat · integrating battery, electronics and propulsion onto a board · keeping wireless control reliable.
It required a complete system able to operate in an unstable, wet and vibration-prone environment.