Home Made Jet Jon ideas

[Frank ZX]

Hi, I have been thinking of doing this for years. Putting a Jet Ski engine and drive on a jon boat.
I have a decent Lowe 1436 boat and I just got a Kawasaki TS650 jet ski. As I started pulling the jet ski apart, I had the idea of cutting the jet ski in half just in front of the engine and attaching the "pod" to the outside of the transom. I'm not sure exactly how I would do it but I think it would have a few advantages over cutting a hole in the bottom of my boat.
What are your thoughts and Ideas?

 

[Frank ZX]

35 views and no ideas? Maybe I'd be better off mounting it inside the boat?
Regardless how I mount it, I will bolt the motor to the boat, then seal with something like 3M 5200 then seal the whole boat with Steelflex. I would love to hear other ideas.
Thanks!

 

[PSG-1]

There's 2 ways of doing it....cut-and-splice (that's where you cut the glass hull out of the ski, and bolt it into the boat) This is by far the easiest and quickest method, and probably the best method if you don't have complex welding and machining equipment.

And then there's the full-out fabrication method, this is where the only part of the jet ski you'll use is the engine and the pump. It's an all-metal construction, including the motor mount system, and the jet tunnel. It's complex, and more labor-involved, but a more durable design for choppy water.

Either method is going to involve cutting a hole in your boat. But the fabrication method allows for reinforcing the area of the cut-out, as the jet tunnel is being fabricated and welded into the boat.

My boat was built with the second method. For a couple of ideas, take a look at my boat build....click the link on my signature.

 

[Frank ZX]

Thanks for the reply PSG-1, I have looked at your boat and I'm very impressed. I have also seen Ranchero50's boat, again very nice work. I understand the 2 methods, and I would have to cut and splice because I don't have the welding equipment but I am a aircraft sheet metal mechanic so I have experience with aluminum,rivets,huck bolts,etc. Unlike most people I don't mind a riveted boat(airplanes are put together with rivets). I feel the most important thing about doing a cut and splice jet jon is how it's attached but more than anything, I worry about Cavitation.
I have read Ranchero50 spoon and it's seems it would help out alot.
This is a third idea of mounting the motor and pump:cut jet ski infront of engine and mount the complete *** end of the jet ski to the transom of the boat. I know this is a wild idea but I'm just wondering if it would prevent cavitation and help from purposing?
The other issue I have is which jet ski to use. I have 2,
1 is a 1993 Kawasaki TS650 and
2 is a 1996 Yamaha Wave Raider 700.
The Kawasaki have lots of cracks in the fiberglass, and a bad starter.(crankcase was under water for how knows how long. and the Yamaha is just well used but runs good.
I have a ton of questions and I want to get this right the first time. I have a Evinrude 9.9 for the time being and I'm still fishing every week so I'm going to finish out the fishing season before I start cutting.

 

[PSG-1]

I would use the Yamaha....as it's a little bigger in C.C. engine size, and it sounds to me that the hull and engine are in better shape.

A lot of people that do the cut-and-splice... cut the hull behind the engine, and use the jet tunnel.

But I don't see why cutting out the entire bottom of the ski and installing it into the boat wouldn't work, either. In fact, that should give you a "spoon" for better handling, and less cavitation.

The trick will be having to do some fiberglass work where you cut the hull of the ski...you'll need to form some type of flange that will bolt into your boat. Also, around the perimeter of the cut-out in your boat, you will need to reinforce this somehow, possibly by riveting or bolting some heavy aluminum angle around the perimeter. This will eliminate a lot of flex, as fiberglass and aluminum have different modulus of elasticity, and anywhere you are joining the 2 together, you want to really beef it up.

But see, I suck at doing fiberglass work, I'm much better at aluminum welding, machining and fabricating....so, the only choice for me was the full-out all metal construction. :mrgreen:

Anyhow, aside from any questions about fiberglass work, I can pretty much answer any other questions you may have as far as building a jet john, as I've done it not once, but twice....first time with a 2 stroke 1000 cc tigershark, and the second time around with a MR-1 HO 4 stroke yamaha.

 

[catmansteve]

I believe the OP is talking of mounting the entire jetski hull, minus the front to the OUTSIDE of the transom so that no parts of the engine/pump are inside the hull of his boat at all.

I am by no means an expert on the subject, having never built an IB jet myself, but I really don't think the idea would work well at all. I can see the positive side would be limited loss of interior space and minimal modification to the boat hull. However, the glaring weakness I see is the boat would only have the narrow ski hull as a planing surface, and the weight of the engine and pump would be levered several feet rearward. My guess is the boat would draft really deep at the rear, and I imagine it would be very difficult to plane, if it would plane at all.

About the only way around this problem I see is to extend the bottom of the boat to the rear of the ski hull, and if you're going to go to all that trouble you may as well just find a bigger boat and mount the engine inside the hull.

Again, I'm no expert and not trying to discourage, just trying to be helpful and point out possible problems

 

[Frank ZX]

Thanks PSG-1 and Steve,
Steve, you understand what I was talking about. It was just a crazy idea. lol
The only way it would possibly work is to know where both crafts would plane before joining the 2 together, and like you said, it still may not plane.
I have watched a lot of jet jon videos and read a lot of negitive. The main problem I see is cavitation with other jet jons. The main 2 that seem to work the best is PSG-1 and Ranchero50 boats.
I have not worked with fiberglass but I have done some major steel metal repairs to Boeing 737, 747,757,767 and 777. Planes float too... well for a little while. lol
I think I will either make if from aluminum or make a flange and joint the fiberglass and aluminum hulls together. The boat is very light and I want to keep it that way. Still in the planning stages but input is welcome.

 

[PSG-1]

Yeah, if you're trying to join the 2 hulls in a manner where the entire jet ski, engine and driveline hang off the back of the boat, it's going to be too heavy in the rear end, and it will likely porpoise. The weight needs to be more forward, so the only thing sticking out the back of the transom is your thrust and steering nozzle assembly.

 

[Ranchero50]

Just for s**** and giggles look at this site ...

https://www.fleetwatermarine.com

Smells like stale spam...

To the OP, I wouldn't try to attach a jet ski hull behind the jon boat. I think the stresses would tear everything apart. As said above, notch out the aluminum hull to fit the bottom and arse end of the ski in and go from there.

Jamie

 

[PSG-1]

Just for s**** and giggles look at this site ...

https://www.fleetwatermarine.com

Smells like stale spam...

LOL, no doubt. That site had absolutely NOTHING to do with the topic at hand.

To the OP, I wouldn't try to attach a jet ski hull behind the jon boat. I think the stresses would tear everything apart. As said above, notch out the aluminum hull to fit the bottom and arse end of the ski in and go from there.

Jamie

Exactly. :mrgreen: