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radryan

  • Karma: +0/-0
11ft home built mini
« on: October 18, 2019, 05:47:41 AM »
Started life as a 18ft kona. Took 2ft out of the center and 6ft off the length. berkeley jet with place diverter, powered by a gsxr 600. Not sure what that combo will do but we'll see. Plan on keeping the 6spd tranny in play
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08chevyguy

  • Karma: +39/-0
Re: 11ft home built mini
« Reply #1 on: October 18, 2019, 07:41:26 AM »
I fuckin love it! Cant wait to see it all come together and see how it does 🤟

Sent from my SM-J727T using SoCal Jet Boats mobile app

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FordLover

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Re: 11ft home built mini
« Reply #2 on: October 18, 2019, 09:55:50 AM »
Wow! How cool is that?

Sent from my LG-TP450 using SoCal Jet Boats mobile app

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radryan

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Re: 11ft home built mini
« Reply #3 on: October 18, 2019, 10:41:14 AM »
Thanks. I just hope the motor has enough to move that pump. Not sure if anyone else has done anything similar
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radryan

  • Karma: +0/-0
Re: 11ft home built mini
« Reply #4 on: October 20, 2019, 07:30:09 AM »
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Got the jet cut in. Back plywood cut @@nd custom spoiler installed. Lol
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mash on it

  • Karma: +29/-0
Re: 11ft home built mini
« Reply #5 on: October 20, 2019, 10:43:50 PM »
Started life as a 18ft kona. Took 2ft out of the center and 6ft off the length. berkeley jet with place diverter, powered by a gsxr 600. Not sure what that combo will do but we'll see. Plan on keeping the 6spd tranny in play

First, I'm not a motorcycle guy.

Second, the gsxr 600 makes between 90 and 110 hp, @ ~13,000 rpm,  depending on year. These figures are from the interwebs.

For a Berkeley pump, with a "C" cut impeller, (the smallest impeller with a detailed chart, from JBP) requires 92 hp @ 3300 rpm, and 110 hp @ 3500 rpm. This is pump shaft rpm.

With the gsxr transmission, 3rd or 4th gear might achieve 3500 pump shaft rpm, with an engine rpm of 13k rpm.

A "C" cut, as well as a "D" cut impellers are not as efficient as an "A" or "AA" cut impellers.

With trying to compare a mini jet boat to a 18' jet boat, it's difficult at best. Let's try.
My boat, 18', Sbc 350, Berkeley "A" impeller, at 4000 rpm, is roughly 45 mph, ~ 228 hp.
With a "C" cut impeller, 228 hp would be about 4500 rpm. The volume of thrust (water) would be similar. So would the speed. (A @ 4000 vs C @ 4500).

2700 rpm is about the slowest I can keep on plane. Somewhere around 22 mph. With a theoretical C impeller thats about 3000 rpm.

Even if your mini jet boat is half the weight, with a "C" cut impeller, at  3500 pump shaft rpm, 35 mph would be full throttle. Possibly 40, but I doubt it, just a wild azz guess. Remember, to achieve 3500 pump shaft rpm, the gsxr will, WILL, be @ 13,000 rpm.

I would go one of two (or 3) different ways-

Keep the Berkeley, and put in a light engine, with double the hp (Think Subaru flat four? 3100 60 GM V6? Ford 2300 turbo?)

Or keep the gsxr, remove the Berkeley, and use a suitable jet ski pump.

Or use an entire jet ski engine and pump. (The aluminum mini jet boat guys have been doing this for years)

I hope this helps.
Others might have more insight than I do.

Dan'l

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CJ/RR 212...under construction  "Pistol Annie"

 


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