Harbor Freight 420cc Predator Engine 10ft Jet Jon Boat (33mph)

[ShallowRipper]

This is a jet jon boat I recently finished with a 420cc Harbor Freight Predator engine (single cylinder, four stroke, air cooled). It pulls up to 33mph with room for a higher top speed, and can tolerate two grown men at over 28mph.

I'll be uploading a detailed build video soon, including a long list of things that could be done better for the next build if anyone wants to try something similar.

I've seen this concept debated, and had wondered for years whether it was worth attempting. I'll try to address any and all questions the forum has in the build video I just started.

 

[BrayD]

We need pics of the hull fabrication and drive arrangement. This is awesome.

 

[MrGiggles]

That is very cool. Did you steal the jet setup out of a Jet ski?

I've wanted to do something similar for a long time, but losing that much floor space is kind of a killer for a jon boat that you would actually use to fish out of. If I did it, I would use a semi-v hull, enclose the front and turn it into a runabout style pleasure boat. Would be a ton of fun to just rip around in, or pull tubes and whatnot.

 

[Crazyboat]

No GPS readout, sitting that far forward doesn't translate into the best possible top end. How many HP does 420 CC produce?

 

[LaqueRatt]

This looks like a thinly veiled advertisement to me.

 

[Mudbugger]

No GPS readout, sitting that far forward doesn't translate into the best possible top end. How many HP does 420 CC produce?

I believe that the 420CC Predator is rated at 13HP. I just finished working on a novelty, parade car that had one for power.

Mud

 

[Crazyboat]

I believe that the 420CC Predator is rated at 13HP. I just finished working on a novelty, parade car that had one for power.

Mud

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.

 

[ShallowRipper]

We need pics of the hull fabrication and drive arrangement. This is awesome.

Thanks, I'm Finishing up the video with the detailed build that should clear up how it was made.

 

[ShallowRipper]

That is very cool. Did you steal the jet setup out of a Jet ski?

I've wanted to do something similar for a long time, but losing that much floor space is kind of a killer for a jon boat that you would actually use to fish out of. If I did it, I would use a semi-v hull, enclose the front and turn it into a runabout style pleasure boat. Would be a ton of fun to just rip around in, or pull tubes and whatnot.

Thank you. Yes this utilized a jet ski pump from an old Yamaha. You're right on point about the lost floor space. It's more of a solo setup, I can fish comfortably with a reasonable amount of cargo. The build you're imagining sounds awesome. There's a group on FB called, "FRANKEN JET JONS" that has some similar builds to what you're describing that came out great. Usually you need 90+ hp jet ski donor to get into the towing territory from what I've observed.

 

[ShallowRipper]

No GPS readout, sitting that far forward doesn't translate into the best possible top end. How many HP does 420 CC produce?

Agreed about the weight distribution! Since I was cannibalizing a 1032 jon boat, it was going to be too much work to move the heavily riveted further seat back. Between the motor, pump, gas, and the passenger, there is a fair amount of weight towards the stern. I can get a GPS readout next time I'm out on the water for anyone skeptical.

 

[Bailey Boat]

I can get a GPS readout next time I'm out on the water for anyone skeptical.

Put me in that category.. A pic of the screen would be best.....

 

[ShallowRipper]

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?

 

[Bailey Boat]

Everything you say above is theoretical, not actual......