How to Make an RC Jet Boat: Pump, Hull and Electronics Step by Step
An RC jet boat moves by pumping water: an impeller inside a duct draws water through an intake in the hull bottom and pushes it out through a nozzle at the stern. Steering comes from turning the nozzle, not a rudder. To make one, you need a hull with a flat-ish bottom section, a water jet unit (bought or 3D-printed), a brushless motor and ESC with water cooling, a steering servo and a radio. Jet boats are great for shallow water because there’s no exposed propeller.
By Kyle HilsonUpdated: October 20264 min read
How a water jet works
The impeller spins inside a tight-fitting housing. Water enters through a grilled intake, is accelerated by the impeller, straightened by a stator and leaves through a nozzle at high speed. The reaction pushes the boat forward. A steering nozzle swivels to direct the jet left or right, and some units have a reverse bucket. Efficiency depends on a close impeller fit and a smooth intake: gaps and rough surfaces waste power.
Parts
| Part | Notes |
|---|---|
| Hull | 40–70 cm; flat or shallow-V where the intake sits |
| Jet unit | Commercial RC jet or 3D-printed design |
| Brushless motor | Inrunner sized for the jet and hull |
| ESC | Water-cooled marine ESC |
| Coupler and shaft | From motor to impeller |
| Steering servo | Waterproof, linked to the nozzle |
| Battery | 2S–4S LiPo depending on setup |
| Radio | 2-channel 2.4 GHz is enough |
Build steps
- Plan the layout: jet at the stern, motor just ahead, battery in the middle for balance.
- Cut the intake in the hull bottom to match the jet’s intake plate; seal it with epoxy or silicone.
- Mount the jet through the transom, aligned straight with the hull’s centreline.
- Mount the motor and connect it to the impeller shaft with a coupler; check alignment carefully.
- Route cooling: many jets have a tap that sends water to the motor and ESC cooling jackets.
- Fit the steering servo and link it to the nozzle.
- Seal everything and fit a watertight hatch.
Testing
Test the jet in a bathtub first at low throttle: water should flow out of the nozzle and the cooling line, and nothing should leak. Then test on calm water near the shore. If the boat porpoises, move the battery forward; if it ploughs, move it back. If the motor gets hot, check the cooling flow. Ready-made jet boats are compared in best RC jet boats.
Tips
- A tight impeller-to-housing fit is the biggest performance factor.
- Use a grille on the intake to keep weeds and stones out.
- Jet boats don’t steer at zero throttle; keep some power in turns.
- 3D-printed jets work but need smooth surfaces and good tolerances.
- Clean the intake after each run.
Why build a jet boat
Jet boats run in shallow rivers and weedy ponds where propellers would snag, and they’re safer around people and wildlife since there’s no exposed prop. They’re usually less efficient than prop boats at the same power, so expect less top speed. A ready-to-run example is the Pro Boat River Jet Boat.
Choosing a hull
Jet boats work best with a hull that keeps the intake in solid water. A flat section or shallow V at the stern lets the intake pick up water without sucking air, which would make the impeller cavitate and lose thrust. Lighter hulls plane earlier and need less power. Many builders adapt a hull from a cheap prop boat, sealing the old shaft hole and cutting a new intake, which is a good first project.
FAQ
How does an RC jet boat steer?
By turning the jet’s nozzle.
Can I 3D-print a jet drive?
Yes, many designs exist; tolerances matter.
Are jet boats faster than prop boats?
Usually not; they’re better in shallow water.
Do they need water cooling?
For brushless setups, yes.
More on this topic: the complete RC Boats guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
