My point is really this, a jet loses a good 30% of it's power compared with a propped boat, to make it equal a propped boat sporting a 9 hp would have to produce 32 MPH, that is a hard sell.
Skepticism in this scenario is a super healthy response I wager. That same skepticism in my mind is what almost prevented me from making this boat. I tossed and turned my share of nights, and decided to take the risk to build it. It would be embarrassing to put a number to the amount of hours I researched, made calls, and calculated the potential for this to work. Between internet research, phone calls, design, tracking down parts, tearing apart 2 jet skis to find healthy pump parts, disposing of jet ski hulls, traveling to find the motor in stock at Harbor Freight, predator motor tear downs/builds/rebuilds, boat modification (cutting, re-riveting), installation of pump assembly, 3D printing the pump/transom flange, turning coupler parts on a lathe, milling motor mounts to spec, there's no less than 175hrs, and at least $2,500 in the build. Joke is partly on me because I put no effort into the aesthetics and it looks like a drunk monkey cut and welded all the aluminum.
I've seen this debated in forums for years, so wanted to share it directly. The final build video is being filmed to help others avoid the same mistakes I made. There's ample room to improve on this design, even things that I still haven't realized that will stick out to a fresh set of eyes and brains.
To potentially quell some skepticism, the power to weight ratio in this case ends up having some critical value to the final speed. The total dry weight of this build including engine, jet unit, and all mechanical/electrical systems is 175lb. The motor is pushing 25+ horsepower, and 5500rpm after some simple but expensive upgrades. If you can imagine at worse case a 20hp prop engine, with the capacity for above stock RPM, on a boat that weighed 75lb, 33 mph with a single passenger should be well within range. Although there is an obvious loss of power efficiency due to the jet drive configuration, the amount of loss for an inboard jet is significantly less than an outboard jet. Hope this helps?
