Building a Jet Jon and i need some help

[walkerwilkin]

I am building a jet jon boat in the coming months. I have a seadoo sp waiting to be torn apart and im still looking for a boat to put the engine in. Im very new here and i would appreciate some advice from some people more experienced than myself.
Questions:
1) V-Hull or flat bottom? Ive heard of cavitation in Jet Jons and i was wondering which hull you all would recommend for a larger lake setting.
2) I was considering mounting the engine to the boat itself and using the fiberglass tunnel off of the jetski and mounting it to the boat. Are there any disadvantages to this or anything I should be worried about with this method? I plan on using an aluminum boat but i have no way to weld aluminum.
I would greatly appreciate tips and advice about any aspect of building this boat.

 

[Ranchero50]

Read, watch and research this site and youtube will answer most of your questions before you even know you need to ask them. For every hour I spent working on my boat I spent 5-6 hours thinking about the work and compromises I'd need to do to make things work well together.

A few guys have successfully built these and they have passed the test of time. A lot of folks have failed and they vanish.

Give us some info about yourself and your abilities to perform the work. Otherwise, too many dreamers out there to waste a huge amount of time and posts on.

 

[walkerwilkin]

Im 16 and this is my project. My dad and Grandfather are machinists by trade. I have help from my father and access to a mill and a lathe and we should have all the necessary experience and tools to get this done. I guess ill just get to work and hope for the best ill keep my build up on here when i start.

 

[Ranchero50]

16 is young, but as long as you have some support and are willing to understand the difficulties involved with this style of fabrication and modification then you may be able to make it work out.

My build is Seadoo based and I tried to go into the details of the how and why I didn't things like I did.

One thing, figure out a budget for your build a at least double it.

 

[PSG-1]

With your dad and grandfather being machinists, you're already off to a good start! However, depending on how you build the boat, some welding will be required, and welding aluminum is a different beast than welding steel.

Check out my aluma-jet build for some ideas. Also, check out ranchero's boat, and painlesstom's build as well, as well as scubapro's jet john. These are 4 jet johns builds on this site that are all excellent builds with lots of good info to help anyone looking to build a jet john.

 

[walkerwilkin]

Is ten foot too short for a jet jon? Just looking for some opinions

 

[PSG-1]

Some of the New Zealand style jetboats are very short, like 10 ft. Just remember that your engine and pump assembly takes up about 4-5 feet of longitudinal space.

 

[Ranchero50]

If you are going for short, just get a 3 seat jetski and do a pole mount on the back.

 

[painlesstom]

Seadoo engine and pump section can be grafted into an aluminum Jon. Flat bottom will be a rougher ride in any choppy conditions, and be more prone to cavitation, but it works fine as evidenced from my build. 10' would be a little short, unless you are just looking to use it to cruise in.. I would recommend 12' if you'd like to be able to move around, also I don't recall seeing any 10 footers that were more than 32" wide... Mine is 12' x 36" and I wouldn't go any smaller if I had to do it again. Another tip is being aware of pump angle when putting things together, vary the angle too much and you can end up with handling issues or planing problems. Building one of these is alot of fun, but it also requires alot of attention to detail to complete reliably. The method I used to build mine would probably suit you best as there is no welding involved, or required. I bolted the Seadoo hull to the Jon boat with 30+ bolts and polyurethane, and then used fiberglass to reinforce the entire engine section to both sides of the Jon hull floor for a larger footprint. Been a year now, over a thousand miles, and not one leak or problem to date. I'll be following your progress and hope to see it turns out as a success.

My FrankenJon -> https://www.tinboats.net/forum/viewtopic.php?f=21&t=28350