Jet john

Post Reply
Paintman
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 30 Jan 2017, 17:28

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
Attachments
20170122_152629.jpg

Paintman
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 30 Jan 2017, 20:20

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?
Attachments
20170130_180203.jpg

Paintman
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 30 Jan 2017, 20:24

Motor doesn't actually attach to the drive shaft
Attachments
20170125_175435.jpg

CedarRiverScooter
Posts: 946
Joined: 13 Nov 2014, 08:01

Jet john

Post by CedarRiverScooter » 30 Jan 2017, 21:35

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
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 30 Jan 2017, 21:58

Thanks for the info,what exactly is cavitation?

User avatar
AllOutdoors
Posts: 209
Joined: 13 Oct 2011, 23:54
Location: Tennessee

Jet john

Post by AllOutdoors » 31 Jan 2017, 00:19

Cavitation is Sucking air instead of water through the pump.

Sent from my SAMSUNG-SM-G870A using Tapatalk
On a shallow river in a RiverPro!

Paintman
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 31 Jan 2017, 00:22

That's what I figured

CedarRiverScooter
Posts: 946
Joined: 13 Nov 2014, 08:01

Jet john

Post by CedarRiverScooter » 31 Jan 2017, 15:18

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
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 31 Jan 2017, 18:47

Ok what is a tapered spoon?

CedarRiverScooter
Posts: 946
Joined: 13 Nov 2014, 08:01

Jet john

Post by CedarRiverScooter » 31 Jan 2017, 19:19

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.
new bottom 002.JPG
new bottom 002.JPG (68.56 KiB) Viewed 4512 times

Paintman
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 31 Jan 2017, 20:32

Cool thanks for the info and help,I'm taking ya'lls advise and molding in the whole bottom part in,
Attachments
20170131_181734.jpg

User avatar
stinkfoot
Posts: 399
Joined: 05 Feb 2016, 03:42
Location: Langley, BC

Jet john

Post by stinkfoot » 02 Feb 2017, 19:43

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
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 03 Feb 2017, 23:04

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

amk
Moderator
Posts: 352
Joined: 01 Jan 2014, 08:52
Location: texas

Jet john

Post by amk » 04 Feb 2017, 12:03

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
Posts: 57
Joined: 30 Jan 2017, 12:21

Jet john

Post by Paintman » 04 Feb 2017, 13:54

Decided to hang the pump out the back so even more room
Attachments
20170204_113617.jpg

Post Reply