My Jet Boat

Out of the box.

at the Christchurch Society of Model and Experimental Engineers in Halswell, I noticed two guys at our boating pond. Curiosity got the better of me, oh well the work can wait anyway, and I found them both running fairly high speed jet boats.

My questions answered I now knew that a toy boat readily available here in New Zealand, could be retrofitted with replacement radio control, a better electric motor and Electronic Speed Controller. Youtube clips provided ample examples of such modifications. Many showed water cooled motors and controllers being fitted. I already had a spare brushless motor and ESC🙂. Within days I had my own yellow jet sprint replica. And yes, out of the box it was very much only a toy. Steering was straight or full left/right. Speed control was ALL or NOTHING, and the boat’s speed minimal.

The jet unit with its new motor.

I took everything existing out of the hull, including the jet/motor unit. Thankfully the glue used did not bond very well, so things came apart easily, including taking the jet unit out. The main reason for doing the latter was that the coupling piece had to be re-bored to match the new motor shaft diameter. Unfortunately I was unable to loosen the damaged hex grub screw holding this onto the impellor shaft. Only by taking it all out of the hull could I tackle this problem. The new motor ( AX2208C-1470Kv Brushless) mounting screws almost matched the existing holes in the jet unit. Only a small amount of filing was necessary to make it fit. The mini servos are u-bracketed down onto supports glued to the bottom of the hull.

I initially tried the boat with a two cell Lipo battery that I have used with this motor/ESC combination before. The resulting performance was only about the same as with the original brushed motor and battery, very disappointing.

However powered by a three cell Lipo, it did give a creditable performance for a model of a jet boat. Sufficient for me in the mean time.

Our dock area, with accompanying ramp, prompted me to have a go at making a boat trailer for the model.  Hence the attempt to make a working reversing bucket for the jet unit. The second servo moves this up and down.

The bucket fitted to the jet unit. I have also extended the nozzle to bring it closer to the bucket.

So far I have had two versions of bucket. The first was my own idea, but it had almost no effect in either backwards motion or steering ability😥.

The second version was made after a friend, Peter Caughey, who drives the real thing, told me what to do. The performance now is amazing. It actually goes in reverse, and it is able to be steered as well🙂. When the steering nozzle goes off centre, the centre wedge re-distributes the water flow to the two water channels.

The original plastic intake grill was in a bad way. I cut it off and replaced it with three lengths of wire inserted into small holes drilled into the underside of the jet unit.

Wooden trailer.

The boat trailer is constructed from scrap timber and the wheels should be on an aircraft. Because of its buoyancy, I had to ballast it with lead strips to keep it on the bottom. I could even use my DUKW, amphibious vehicle, to tow it to the water.

The radio set that I purchased to go with this model happened to be Mode 2. Having become used to Mode 1 (rudder and throttle) on the right, with other boat models, I proceeded to change the sticks around. In the process I had to swap over the potentiometer wires. I chose to substitute a toggle switch for what would have been the left stick up/down movement. This now gives me full travel in both directions suitable for the bucket operation.

I may yet give the model a new paint job complete with an original name.

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