# Possible Jet ski Powered Aluminum Skiff. Seadoo or Jetski?



## Hollywood1 (Jun 29, 2012)

Just got back from a weekend at a Local Southern California Lake and renting a 14ft. aluminum boat with a 6HP outboard to do some fishing. Unfortunately, I got skunked with no fish. But it turned me on to looking into getting my own aluminum boat so I wouldn't feel pressured to have to get the rented boat back in time. 

Then I came across the Jet ski powered Skiffs and Jon boats. Wow! Im hooked on wanting to build one of my own now. It would be nice to get to more parts of the lake in a faster period of time let alone have some fun while doing it.

My question is, what size jet skis or sea doo are good candidates? Im a Metal fabricator but would like to do the least amount of Aluminum welding as possible. So looking at something to where I could cut out the hull of the jet ski and swap it into the aluminum boat, then seal it up from there. I know its not as easy a swap as I just made it sound and it will take some good engineering along the way. 

Eventually I'll platform it and make it a good and little Bass worthy boat for the local Southern California lakes and maybe even Long Beach Harbor.

My Uncle has a 14' aluminum Skiff that has a Vhaul in front then tapers to flat in the rear. My buddies dad has a GTX Seadoo that has been seating for about 3 years, which I might be able to work out a trade for some residential Iron work, which is what most of my business is. 

I have also found some 650 stand up jet skis on CL for under $1000. Im not sure if its easier to just pop in a 650 smaller jetski engine or to tackle hacking up a perfectly fine bigger GTX sea doo? I haven't been able to find any wrecked Sea doos yet, the summer is still pretty early.

Any insight would be greatly appreciated.

This is the video that got me started on the PWC powered boat research.

https://www.youtube.com/watch?v=xnJI0cKLh5E


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## PSG-1 (Jul 1, 2012)

I'd go with at least a 700 cc engine or larger for a 14 foot boat. While a boat may not weigh as much as a jet ski, there is more hull surface in contact with the water, which means it will require more power to run the same speed as a small, narrow jet ski of the same weight.

Check out my youtube channel for some ideas on jet ski johnboats...as well as my thread on the Aluma-Jet.


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## Hollywood1 (Jul 2, 2012)

Thanks PSG-1.

Im not to familiar with the CC size on Jet skis and SeaDoos, most of the Seadoos I saw on Craigslist only show model numbers and not CC's. I'll have to research the cc's of the more common Sea doos.

The stand up Jet skis are much cheaper, but have only seen them in the 650cc range.


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## PSG-1 (Jul 3, 2012)

Hollywood1 said:


> Thanks PSG-1.
> 
> Im not to familiar with the CC size on Jet skis and SeaDoos, most of the Seadoos I saw on Craigslist only show model numbers and not CC's. I'll have to research the cc's of the more common Sea doos.
> 
> The stand up Jet skis are much cheaper, but have only seen them in the 650cc range.



Kawasaki makes a 750 cc stand-up jet ski.....that's what I used to ride before I went to a Yamaha Super Jet....those are 700 cc engines. 

Now as far as the installation of your engine and pump.....there's 2 ways to do it. Cut and splice (easy) or a full out fabrication (more difficult, but much more durable) Cut and splice is when you cut the hull out of the jet ski, with the engine, pump, etc....then you splice it into your hull. This works fine if you're planning on running in flat water with no chop.

But if you're planning on being in the ocean, rough water, etc....then you should consider all-metal construction. To do that, you'll need to find a jet ski that uses a bolt-in aluminum intake duct, or you'll have to buy this pump assembly seperate. The Yamaha XL800 and a few models of XL1200 use the bolt-in duct. All other jet skis have the duct molded into the glass hull.

If you use seperate components....i.e., a Kawasaki engine and a Yamaha pump, you'll have to figure out a way to couple them together. The easiest way is with a spartan jaw coupler, like those used on the 750 Kawasaki jet skis, or some of the Yamaha engines. 

You may have to take a factory coupler, and modify the bores, then re-thread them, to fit the particular thread pattern of the PTO and pump setup you are running with. If you have to go with a larger bore, that's easy, you just drill it out and thread it. But if you have to go with a smaller bore, then you'll have to drill it out, weld in a piece of 1 inch solid aluminum round stock, then re-drill and thread it for the size you need.

Anyhow, keep us posted. If you run into any difficulties, I'd be glad to give some advice, as I've done this not once, but twice....the first time with a 2 stroke Tigershark 1000 engine, then with a Yamaha MR-1 high output 4 stroke. So in other words, I pretty much know about every quirk and idiosyncrasy you could possibly run into.


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## Hollywood1 (Jul 10, 2012)

Awesome PS! Thanks for the insight. I'll be back when Im ready to get started. 

It would be nice to just be able to splice it into a skiff and hit the water. But I would eventually like to Ocean it and you never know how the Seas can get. Maybe I'll do a splice in for my first one and reinforce the aluminum material where the connection is so there will be less warping in the usually thin aluminum skiffs.

Thanks again!


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## PSG-1 (Jul 11, 2012)

Hollywood1 said:


> Awesome PS! Thanks for the insight. I'll be back when Im ready to get started.
> 
> It would be nice to just be able to splice it into a skiff and hit the water. But I would eventually like to Ocean it and you never know how the Seas can get. Maybe I'll do a splice in for my first one and reinforce the aluminum material where the connection is so there will be less warping in the usually thin aluminum skiffs.
> 
> Thanks again!




No problem. Like I said, the cut and splice method is always the easiest and cheapest route to go, and there have been quite a few jetboats built like this that run just fine. But if you plan on hitting the ocean, or any other choppy water, you'll want the all-metal construction for peace of mind, as aluminum and fiberglass have a different modulus of elasticity, and different yield strengths, when you start beating the assembly around in choppy water, the spliced hull has more potential for problems, particularly right at the joint, and even more so right at the fasteners, such as bolts.

But, if you can find a way to reinforce that connection, it would probably be OK.

If you're planning on the ocean, you DEFINITELY want a welded-bottom boat, not a riveted bottom, as the welded bottom is going to be around .090" thick.....riveted bottoms are usually .062" or sometimes thinner....and riveted bottom boats are notorious for leaks, especially when operated in salt water, or rough water conditions.


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## Buddychrist (Jul 11, 2012)

PSG-1 said:


> Hollywood1 said:
> 
> 
> > Thanks PSG-1.
> ...







I had traded a kawi 750cc and let me tell you with a coffman exhaust those things are FAST


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## PSG-1 (Jul 11, 2012)

Yeah, the 750's are fast little skis. I started riding way back in 1986, on the old 550's.

But out of all the skis I've owned, the Super Jet has been the most durable, no stress cracking on the hull or handlepole, even with the way I ride (and if you've seen my youtube videos, you know I show a ski no mercy)


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