rear cockpit jet drive...

About using jet ski motors to power small boats

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gwmichie
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rear cockpit jet drive...

Post by gwmichie » Tue Jan 12, 2010 5:33 pm

lots of discusion on this subject guys but i cant seem to find just what im looking for. I would like to do a rear cockpit with a jet drive. Seems like the drive line could be extended to run threw or under the cockpit to drive the pump. I plan on using a rotax motor out of a seadoo, from what i have seen in PWC this puts the drive-line about 7 inches above the bottom of the boat. what could i do to lower this drive-line?? some type of two piece set-up??? any suggestions would be great.

thanks
gw

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Mr Hot Rod
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Re: rear cockpit jet drive...

Post by Mr Hot Rod » Tue Jan 12, 2010 6:36 pm

Which boat ?? Tiny Might ??
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Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod : http://www.boats.chelseacoachworks.com

gwmichie
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Re: rear cockpit jet drive...

Post by gwmichie » Fri Jan 15, 2010 6:08 am

i have a set of crackerbox prints, but depending on the PWC I end up with it could very easily end up being a tiny mite design, or a combination of the two. Hull depths of both are very similare so the same "debth of driveline" issue is going to apply.
I would love to find one of the 250hp rotax motors but price is probably going to have me settle down in the 130-150 range. more than enough for a tiny mite, but maybe a little underpowered in a cracker??
I have seen pics of older ski boats running a driveline to the pump, just dont know if there is a reason you dont see this much anymore??

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Mr Hot Rod
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Re: rear cockpit jet drive...

Post by Mr Hot Rod » Fri Jan 15, 2010 11:53 am

The Cracker Box and Tiny Might cockpits are pretty narrow to start with. At 7" above the keel, a torque tube would be at or slightly above the tops of the engine stringers. Here are some pics of a TINY MIGHT built by Robert Hankins, Fresno, CA. It's powered by a 120 H.P. Honda Civic engine. I'd mock up the cockpit to see if there's enough room ...
  • Image Image

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If you want to drop the torque tube any lower, you'd have to step up to a longer boat (Cracker Box) and use a Casale Parallel Z-Drive. This would put you about 4" above the keel and allow you to pick your gearing. Going this route would beg for a V6 installation but I don't think the pump would hold up.
Several transmission manufacturers offer drop-center transmissions but these would provide very little drop, reduction gearing, redundant F/N/R gears and excessive weight.

Either way, you'll have to contend with hull balance issues as noted in previous Cracker Box threads. I've got my new Flame Suit on, so I'm good to go !
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Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod : http://www.boats.chelseacoachworks.com

matt
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Re: rear cockpit jet drive...

Post by matt » Wed Jun 02, 2010 7:46 pm

i'm going the same route with my tiny mite build, jetski power, rear cockpit. i've been thinking of sitting ON the boat instead of IN it? side-by-sides are very popular in the atv world, i'm thinking of making my tiny mite the worlds first side-by-side jetski :wink: i think it would look and function really well. dual console like the newer nitro bass boats but with jetski seats behind them, but which side should i put the controls on? or i could just do a center console farther forward with a longer seat? i need some feedback on this, this could snowball into something very unique 8)

upspirate

Re: rear cockpit jet drive...

Post by upspirate » Thu Jun 03, 2010 6:32 am

well here is a side by side jet ski,but it wouldn't have a hull like yours!!!(I'd like yours better!! :wink: )
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92_Kawasaki_SC_Side-Side_2_.JPG (9.91 KiB) Viewed 7554 times

matt
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Re: rear cockpit jet drive...

Post by matt » Thu Jun 03, 2010 1:23 pm

i knew if i said "worlds first" i would get a picture of one the next day, i love it when a plan comes together. the helm on that thing is in the center, so it may not be a side-by-side, it may be the fata$$ski :lol:

upspirate

Re: rear cockpit jet drive...

Post by upspirate » Thu Jun 03, 2010 1:35 pm

I knew about that model cause a friend has one.

The steering console is interesting as it slides to the side for two people on it,or in the center for one

matt
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Re: rear cockpit jet drive...

Post by matt » Thu Jun 03, 2010 5:58 pm

ENGINEERING at its finest, i love it :D

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