# Jet john



## Paintman (Jan 30, 2017)

New to this forum,seems to be a lot of info here,just starting a jetboat project and have tons of questions,this is what I'm starting with,kawasaki 750ss and a 15 foot terry flat bottom


----------



## Paintman (Jan 30, 2017)

I see a lot of guys put the whole bottom of the ski in the bottom,I was wondering why I couldn't just cut out the intake portion where I have it circled and just mount that along with the jet and do motor mounts seperate?


----------



## Paintman (Jan 30, 2017)

Motor doesn't actually attach to the drive shaft


----------



## CedarRiverScooter (Jan 30, 2017)

Hey Paintman - Looks like a great start to your project.

The advantage to installing the whole length of jet ski bottom is that the mounts & alignment is pretty much setup for you. Saves a bunch of work. The fiberglass is pretty stiff too.

I have found that the pump inlet needs to be set deeper than just flush with the hull bottom, to eliminate cavitation.

Keep us updated with lots of pictures. You're gonna have a blast!


----------



## Paintman (Jan 30, 2017)

Thanks for the info,what exactly is cavitation?


----------



## AllOutdoors (Jan 30, 2017)

Cavitation is Sucking air instead of water through the pump.

Sent from my SAMSUNG-SM-G870A using Tapatalk


----------



## Paintman (Jan 30, 2017)

That's what I figured


----------



## CedarRiverScooter (Jan 31, 2017)

I originally set mine in flush, & it would cavitate (engine just revs up, no thrust) with anything above a 1 inch chop.

Pretty miserable ride back home when the wind kicks up.

I took it back apart & have it set down a couple inches, along with a tapered 'spoon' panel to accomodate the transition.

Now a 3 inch chop is no problem. Anymore than that & I don't want to be out in a jonboat anyway.


----------



## Paintman (Jan 31, 2017)

Ok what is a tapered spoon?


----------



## CedarRiverScooter (Jan 31, 2017)

A spoon is a bump on the bottom of the hull, in front of the intake, which diverts air away.

I recommend reading threads from Ranchero50 & PSG1, they are the experts.

Here is a picture of my version. It is not really spoon shaped but works for me.


----------



## Paintman (Jan 31, 2017)

Cool thanks for the info and help,I'm taking ya'lls advise and molding in the whole bottom part in,


----------



## stinkfoot (Feb 2, 2017)

Meanchicken.net also has some interesting and useful jet jon info. I have a 16 foot jon with a 40hp Merc. Have often thought of putting a ski motor in it but it sure eats up the room when your boat is that small.


----------



## Paintman (Feb 3, 2017)

Way I got it figured my motor won't be that far foward


----------



## amk (Feb 4, 2017)

im not sure about for that exact motor but they make diferent intermediate shafts so you can definetly shorten the gap from the motor to pump. Specifically any motor that was put in a stand up ski will have the short shaft. Your motor mounts are very close the intake so you have a pretty short skid as it is. Make sure you seal everything really tight and well its no fun to get it all built and have to tear it back down again.


----------



## Paintman (Feb 4, 2017)

Decided to hang the pump out the back so even more room


----------



## amk (Feb 5, 2017)

that's how mine was set up worked just fine.


----------



## CedarRiverScooter (Feb 5, 2017)

You could tie into those two ribs that will be directly under engine. Would take some careful dissection with a cutting wheel, to expose the hull skin for the insert to lay flat.


----------



## Paintman (Feb 5, 2017)

Got the hole cut


----------



## stinkfoot (Feb 5, 2017)

I recommend a window screen and a coupla cans of Flexseal! :LMFAO:


----------



## huntinfool (Feb 6, 2017)

Sup bro? See you in 2 weeks. Welcome.

Here is my dad's project 









I'll try and find some in construction pics later. Gotta work now. 

Sent from my XT1585 using Tapatalk


----------



## Paintman (Feb 6, 2017)

Cool,ya bringing it to grxh?


----------



## Paintman (Feb 6, 2017)

Think it will cavitate?


----------



## stinkfoot (Feb 6, 2017)

Paintman said:


> Think it will cavitate?



WOW you sure knock this stuff out quick, Paintman! What are you going to seal the ski/hull interface with?


----------



## Paintman (Feb 6, 2017)

Still researching that


----------



## Paintman (Feb 6, 2017)

I'm guessing 3m 5200 may be the way to go


----------



## huntinfool (Feb 6, 2017)

No sir, I'll be bringing my boat. 
Here are a few more pics. He cut the boat in half and welded in an additional 22" of aluminum. That was the width of the pod he.put in with to motor on it. 

























Don't know if any of these will help. 

Sent from my XT1585 using Tapatalk


----------



## stinkfoot (Feb 7, 2017)

Paintman said:


> I'm guessing 3m 5200 may be the way to go


 I think you may be right. Wish they made an aluminum ski you could weld in. Good luck! Don't dismiss some of the flexible epoxies.


----------



## huntinfool (Feb 7, 2017)

We bolted our pod in with 5200. Used it to seal all of the remaining areas too. The leaks we had appear to be areas where the 5200 wasn't applied at all or not thick enough. 

We actually didn't have any leaks around the pod, just at all the other points. 

She should be ready for another test. 

Sent from my XT1585 using Tapatalk


----------



## CedarRiverScooter (Feb 7, 2017)

Paintman, that install looks great. Shouldn't cavitate!

The 5200 is pretty runny & on my 1st install it ran out overnight, esp. at the transom vertical seams.

On my redo, I taped the seam from underneath to hold the 5200 in. I used some 1/8 plastic spacers (inboard of the caulk) to hold a consistent gap. At the transom, I taped it up both sides a couple inches at a time. I did the transom top seam separately.

I used 2 caulk cartridges of 5200, probably was overkill.

I would scuff the hull alum with 80 grit right before you do the install.

Leaks can be hard to pinpoint later!

I have mine cross-bolted to the internal bracing, so no screws go directly thru the hull.

Good luck


----------



## Paintman (Feb 7, 2017)

Will fiberglass work for smoothing the bottom and the nose portion


----------



## SC Designs (Feb 8, 2017)

Yo Paintman, check out my latest build I just posted. I seal everything with 3M 5200 and stainless screws then come back over it with fiberglass and bondo for smoothing.


----------



## CedarRiverScooter (Feb 8, 2017)

I also used fiberglass filler for smoothing. I recommend epoxy resin for the fiberglass filler. Polyester can absorb water & has less adhesion to boot.


----------



## stinkfoot (Feb 8, 2017)

What happens when you nail a rock with the Bondo?


----------



## SC Designs (Feb 9, 2017)

The bondo is very small amounts, basically when the glass is laid it still creates and uneven surface so after sanding you still have high and low spots, that's where the bondo comes in. Its not large amounts to fill up huge holes. It's a given if a person smacks a huge rock, no matter whats under there on the hull, it stands the possibility of doing damage. I personally try to stay away from the rocks...lol.


----------



## Paintman (Feb 12, 2017)

Little work done


----------



## Paintman (Feb 12, 2017)

More progress


----------



## Paintman (Feb 12, 2017)

Some more pics


----------



## SC Designs (Feb 13, 2017)

Looking Good !!! =D>


----------



## CedarRiverScooter (Feb 13, 2017)

Great job!

Transition panel should work good to avoid cavitation.


----------



## Paintman (Feb 21, 2017)

Jet fitted


----------



## Paintman (Feb 22, 2017)

Little work


----------



## flex (Feb 22, 2017)

Hey buddy! Haha. I also joined to post my build!

Sent from my HTC One M9 using Tapatalk


----------



## Paintman (Feb 22, 2017)

Awesome,what r u building


----------



## handyandy (Feb 23, 2017)

So are the pump housings on those jet skis composite with a metal wear sleeve in them?


----------



## Paintman (Feb 23, 2017)

No all composite,the jet is aluminum


----------



## Paintman (Feb 23, 2017)

Ready for primer


----------



## CedarRiverScooter (Feb 24, 2017)

Paintman - looking great! What type of paoint are you going to use?

Handy Andy - The PWC makers all had their own designs.. My Polaris has an aluminum wear housing. My friend's Sea Doo had a plastic wear ring insert. Some makers used stainless steel, or at least it was an aftermarket part.

Sucking up sand & gravel definitely chews them up!


----------



## Paintman (Feb 24, 2017)

Gonna use this on the bottom


----------



## Paintman (Feb 25, 2017)

Looks like factory


----------



## SC Designs (Feb 27, 2017)

Looks great, you are definitely heading in the right direction !!!!


----------



## Paintman (Mar 9, 2017)

Wetlanders slick bottom


----------



## stinkfoot (Mar 9, 2017)

Be interested how that holds up versus my Goop Coat-it. What kind of rivers are you on Paintman? I am usually on small round granite in the rivers round here..


----------



## Paintman (Mar 9, 2017)

Mostly submerged logs that like to break lower units


----------



## stinkfoot (Mar 9, 2017)

Paintman said:


> Mostly submerged logs that like to break lower units


 Should slip over them nice and easy then. Mine is already getting scratched up.


----------



## Paintman (Mar 9, 2017)

Check out wetlanders www.bottomcoatings.com


----------



## Tman (Mar 10, 2017)

Paintman said:


> Wetlanders slick bottom



did you use the primer also or just a topcoat kit?


----------



## Paintman (Mar 10, 2017)

Primer as well


----------



## Paintman (Mar 14, 2017)

Ready to flip back over


----------



## Paintman (Mar 14, 2017)

One more pic


----------



## CedarRiverScooter (Mar 15, 2017)

Really smooth spoon!

Where does the exhaust exit? In tunnel?

Also, will you have a ride plate?


----------



## Paintman (Mar 15, 2017)

Not sure on either yet,got it flipped back over


----------



## huntinfool (Mar 16, 2017)

Paintman said:


> Looks like factory


Come on Granger! About ready for a test run. 

Sent from my XT1585 using Tapatalk


----------



## Paintman (Apr 2, 2017)

I'm using a Kawasaki 750 as motor and was wondering if I could attach a waterhose to the intake hose so I could test run at home,also where should I run my exast,out the bottom or out the back?


----------



## flex (Apr 2, 2017)

Paintman said:


> I'm using a Kawasaki 750 as motor and was wondering if I could attach a waterhose to the intake hose so I could test run at home,also where should I run my exast,out the bottom or out the back?


Yes to the hose. Just don't rev it to much. I would run the exhaust out the back. So if it leaks you don't sink and it's an easy fix. Make one of those pee streams too!

Sent from my HTC One M9 using Tapatalk


----------



## CedarRiverScooter (Apr 2, 2017)

Not sure about a Kaw, but on Polaris you are supposed to start the motor 1st then turn on garden hose. Apparently water can backflow thru exhaust ports if motor isn't running 1st.

I'd get the exhaust to be as low as possible, as it will be loud. Make sure it routes above max waterline, so it can't siphon water.


----------



## Paintman (Apr 3, 2017)

I'm thinking about using a flexible radiator hose for the exhaust, the rubber hose from the ski won't work,what says the jet john guru's


----------



## CedarRiverScooter (Apr 3, 2017)

As long as it is same diameter, should work. It doesn't get very hot since it is water cooled exhaust.


----------



## Paintman (Apr 5, 2017)

Got the exhaust run tonight,and fired it up,need to rebuild the carb,only way it would fire was pouring gas down the carb,can anyone post a pic as to where all the hoses go,


----------



## CedarRiverScooter (Apr 5, 2017)

'Green Hulk' is a great website for PWCs. They will have the info you are looking for. I got a shop manual for my Polaris, that is very helpful.

On the carb rebuild, get an OEM kit, the aftermarket ones are junk. Consider a new fuel pump. It it goes lean you will burn pistons up.


----------



## Paintman (Apr 11, 2017)

Motor is running good,started on the rear deck tonight


----------



## Paintman (Apr 15, 2017)

Little more work,seat area is removable along with the deck


----------



## Paintman (Apr 19, 2017)

Struggling with steering,any help


----------



## flex (Apr 19, 2017)

Paintman said:


> Struggling with steering,any help


I think most of the converted jet boats I've seen use a "stick steer" like an air boat.

Sent from my HTC One M9 using Tapatalk


----------



## Paintman (Apr 19, 2017)

Ya I didn't wanna do a stick steering


----------



## CedarRiverScooter (Apr 20, 2017)

Are you going to use jet-style 135 degree helm?

https://www.wholesalemarine.com/teleflex-sh5087p-jet-boat-135-steering-helm.html?gclid=COrOnfv6stMCFca1wAodr8UBNg

You might have to get a custom cable too.


----------



## Paintman (Apr 22, 2017)

Lake tested,a little cavitation,hoping the front deck will help,was really rough on the water


----------



## Paintman (May 3, 2017)

Headed to the lake friday,finally finished the decks,all aluminum


----------



## CedarRiverScooter (May 4, 2017)

Looks great!

What did you end up doing for a steering helm?


----------



## Paintman (May 4, 2017)

Used the helm that came with the console,get a turn and a half on the steering wheel


----------



## Paintman (May 9, 2017)

Anything over half throttle cavitates some,gonna need a spoon,anybody have any designs,this is what I came up with


----------



## Paintman (May 9, 2017)

Started working on a spoon design2


----------



## Paintman (May 9, 2017)

No idea if this design will work,any feedback would be greatly appreciated


----------



## CedarRiverScooter (May 9, 2017)

Looks like it should push the air out of the way! How did you form it?

But kinda reminds me on my 1st attempt at a spoon, which didn't work.

Here is a picture of my epic fail, good thing it was just a prototype:





The problem with that one was it was too abrupt.

On my next try, I made a long shovel, it has a slight Vee to it. Now I can handle up to 3 inch chop.

If it is cavitating in glass smooth water, it may be the the pump shoe isn't sealed well.


----------



## Paintman (May 9, 2017)

Hammer and dolly,and anvil,aluminum was already somewhat curved when I started


----------



## Paintman (May 9, 2017)

Mine isn't near as abrupt,pics are hard to take from the bottom but I think the transition is pretty mild


----------



## Paintman (May 13, 2017)

Put a solas concord 9/15 pitch impeller on and it made a world of difference, don't think I'll even need the spoon now,hardly even cavitates in 4 inch chop


----------



## CedarRiverScooter (May 13, 2017)

Good to hear!

Got mine out for 1st time this year. What a blast.


----------



## Paintman (Jun 11, 2017)

Well pretty well finished up,painted and all


----------



## SC Designs (Jun 12, 2017)

Looks Awesome !!!!!


----------



## CedarRiverScooter (Jun 12, 2017)

+1

The high transom looks awesome.

Does Shep get to go along?


----------



## Paintman (Sep 11, 2017)

My manual adjust trim nozzle,no more pourposing


----------



## CedarRiverScooter (Sep 13, 2017)

Can you measure how many degrees down (from hull plane) you ended up with?

Looks like maybe 7 or 8 but hard to tell from a photo.


----------



## Paintman (Sep 13, 2017)

It at the farthest point in the picture,I'm going to adjust it upwards next time I take the boat out,just trial and error I guess


----------

