KY JetJon Project

Well having been a lurker and a somewhat infrequent poster, I have finally put my money where my mouse is (that was a forum pun....). I now have in my garage a chopped up jetski and a "new to me" jon boat. The jetski is a Kawasaki 750 STS 2-stroke powerplant pushing 70hp, and the boat is a Lowe 16' flat bottom jon with a Johnson 70 horse on it.....yes, I said 70 hp. The boat is actually 15 ft something and I do believe the CG sticker calls out a 50 hp max rating, however I do not think the previous owner could read or feel fear. While I haven't had the boat out on the water yet with the 70 hp outboard (motor repairs) I am guessing that little boat will hit the upper 40's maybe 50 mph, whatever it does it should be interesting. The goal of the build is to produce a shallow water runner that will get me and my two boys closer to the fishing holes.

I am expecting roadblocks and hurdles, however I feel confident in you the reader's ability to walk me through it... :LOL2: Just kidding...I have been doing a lot of reading and researching so hopefully the bumps will be minimized. This will be a glue and screw build, maybe once I have cut my teeth on the first jetjon I will do a full-on build like Ranchero and PSG-1 at a later date. I'll post up pics and progress as she goes, so feel free to offer advice or whatever.

here are some pics so far

cutting up the ski, and how she sits now. Once I get the boat ready, I will finish chopping up the jetski hull.

The boat...what a mess. There was about 100 lbs of wet lumber in the front platform area of this boat. I removed enough exterior screws to build a deck with....some people shouldn't own boats. Oh, and by the way if you ever get a bright idea to build your own livewell out of OSB and fiberglass....don't. I don't even think the fish appreciated this mess.

This was after a couple hours of deconstruction work on the boat. I did get the Johnson 70 hp running, so it will be going up for sale to offset the cost of the boat hull.

Looking forward to seeing the build. Man that boat had some weight up front with all the wood, no wonder he was running a 70, he needed it to get on a plane.

With all the wood gone and the hull empty, this little boat should skip across the water. I am planning on testing out the outboard today, just have caulk all the little screw holes some moron made while building a deck on the boat.

Tested outboard today....took awhile to get it started, then it was fine at idle but would bog down anywhere past that. I could get the motor to respond to the electric choke when it was bogging but I couldn't get it past 7mph or so. Guess it's back to the garage to clean out the carbs and adjust linkage . As soon as this outboard is running correctly it will be sold and I can start working on the jet part of the jon boat, but until that happens I have nowhere to put the outboard.

One issue I have been trying to work out is how far back can I mount my jetski in the boat hull...On the kawasakis there is an exhaust hose terminating right next to the pump area as well as a drain plug on the other side. I don't think there is enough room to cut next to them to make a "tunnel box" to stick out the back of the boat in order to push the rear end of the ski past the transom of the jon boat (see picture). I may have to make the back of the ski flush with the transom of the boat, will this cause any planning or driving issues?

The reason I ask, is that most jetjons I have seen have the ride plate and pump housing extending well past the transom of the boat. Thought maybe there is a reason for this.

Check out you tube and watch jet Jon the hard way by captainron. He had a jetski hull like yours. It may give you some ideas. I did not know where mine was going to sit until I had it in the boat.

On mine when it was a shorter hull without the pods the pump would stick out the back it would last and settle with a lot of angle. Not something you want in shallow water. With the pods the boat planes and settles really flat. I may have lost some maneuverability but not enough to be an issue in an emergency.

In other words, I wouldn't sweat it as long as the front of your hull is heavy enough to keep the jet from sucking water. And if it does, make a spoon.

Well I am dead in the water until I get this hunk of aluminum and steel off the back of my jetjon...more outboard issues to work on...but at least two boys and a furry best friend are enjoying the boat in the meantime :wink:

While I am impatiently waiting on outboard parts....FOR 4 DAYS NOW!!!.....I decided to start messing around with the interior of the jon hull. I began by pulling up the front aluminum floor and found water logged foam, there had to be at least 40 lbs of wet white foam in the front of the boat...so out it went and in went pink closed cell foam from home d-pot. After that debacle I started pulling what carpet I could from the sides of the gunnels and ran into a very messy carpet glue job. Whoever installed the carpet wasn't taking any chances, there was at least an 1/8" of dried hard carpet adhesive that no solvent would touch...I tried them all. In the end a scraper with a utility knife blade scraped and chipped it all away (not looking forward to the large floor area covered in carpet ).

Found a good way to fix holes in the aluminum boat, went to harbor freight and picked up some alumaweld rods and started filling all the screw holes along the edge of the hull, worked out nicely and I didn't have to use anymore rivets!

Any updates on the motor? I would like to see how long you hold it at full throttle before self preservation kicks in.

A friend of mine has a 70hp Yamaha on a 16' Lowe - dunno if it's flat bottom or semi-V I didn't see it out of the water and the decking obscures any view of the bottom. It has a center console and was very stable even at full throttle...I didn't have a GPS or anything with me, but I wouldn't guess it did more than 35 / 40 mph, maybe 45 absolute max...

I've got a 20hp on a 1436 which everyone said would be a missile - it only does 28mph. Fast enough for sure, and I'd never run it that fast on rough water, but on any body I fish it's just fine.

Fuel pump supposed to arrive tomorrow. Once I get that hooked up I will test it out again for the 3rd time and I am praying that this solves the bog issue....just have to wait and see.

I will take a video with the phone, however I don't know how to upload it to youtube? I would also like to know for the upcoming jetjon build so everyone on here can enjoy the build in high definition!

Well long time no post..... I sold my outboard and am now working on the jetjon. I have the ski bottom cut out and installed into the boat hull, I used 4 tubes of geocel pro flex polyurethane sealant and 12 carriage bolts to mate the two surfaces. Unfortunately the geocel caulking doesn't like gaps over 1/2" and is taking forever to cure out, its been 4 days or so and its still real soft, but slowly stiffening. I haven't had a chance to water test the seal but I might back the boat into the water this weekend just to see how bad she leaks, more or less a float test. I am also wanting to fiberglass the bottom of the hull and jetski for a better bond but I not sure how fiberglass will do over a caulked seam, I wouldn't think the resin would stick to caulking?? Any suggestions? I will post up a video showing the install for you guys to take a gander at. Really looking forward to testing out the engine.

Here's a video update https://youtu.be/97Ug8BFQJrc

I am guessing I need to supply fresh air into the engine compartment, any good ideas on how to accomplish this? I will pretty much cover the entire back portion of the boat using aluminum angle with a 3/8" MDO sheet (about the same weight as aluminum) and it will be hinged across the back to open as one unit to access the engine, gas tank, battery etc... I was thinking about a small scoop turned backwards towards the transom similar to an inboard boat. As to the size I need not sure :?:

I did recessed air vents on the front edges up my engine, mounted green lamps in them and the choke / fuel select. I also have a 6x6" opening under the drivers seat where I had to brace the mount.



In the rear I installed an old computer tower vent in the back of the dog house. I am still missing one of the rear hatches but figure this setup should work well. I seldom if ever smell any fuel fumes either at the ramp or on the water.

Ok, that's clear enough. I will mount two raised vents towards the transom and a couple of round vents under the driver seat on the bulkhead, that should give me plenty of fresh air. The original jetski had much less air intake than what I am installing so I should be good.

Bought 100 lf of 1.5" aluminum angle today...$160! :shock: I'll post up progress pics of the deck framing, my goal is to just get the driver area framed in so I can mount steering and controls for a test run to figure out the balance of the boat. Hopefully by the weekend!