Jet john

[Paintman]

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]

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]

Motor doesn't actually attach to the drive shaft

 

[CedarRiverScooter]

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]

Thanks for the info,what exactly is cavitation?

 

[AllOutdoors]

Cavitation is Sucking air instead of water through the pump.

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[Paintman]

That's what I figured

 

[CedarRiverScooter]

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]

Ok what is a tapered spoon?

 

[CedarRiverScooter]

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]

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

 

[stinkfoot]

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]

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

 

[amk]

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]

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

 

[amk]

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

 

[CedarRiverScooter]

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]

Got the hole cut

 

[stinkfoot]

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

 

[huntinfool]

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.

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