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10-06-2018, 10:23 PM
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#1
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Guru
City: Ingleside-On-The-Bay, Texas
Vessel Name: Papillon
Vessel Model: 1978 Mainship 34 Trawler #95
Join Date: Jan 2018
Posts: 643
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small jet ski engine?
I am looking for specs for the smallest jet ski propulsion system I can find to use in a 10' dinghy for my trawler. Lightest possible weight. the dighy will carry two people plus groceries. Hopefully. from a model no longer in favor that I can pick up as junk.
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10-07-2018, 01:11 AM
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#2
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Guru
City: Fort Lauderdale. Florida, USA
Join Date: Jan 2014
Posts: 21,449
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Also, for your information, SBT carries a huge selection of remanufactured jet ski engines and systems.
Will be interested in seeing how your conversion works as we are strong proponents of jet RIBS.
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10-07-2018, 06:33 AM
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#3
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Guru
City: Northport
Join Date: Aug 2015
Posts: 2,046
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10' will not accommodate any jet ski or rib-jet engine/drive combinations that we are aware of. It lacks both size and weight capacity for the units but perhaps a smaller unit with less hp from the newer surfskis might work.
https://www.amazon.com/Motorized-sur.../dp/B078K4D9X4
IMHO - a jet drive is more complicated, heavier, less efficient and has less control than an outboard.
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10-07-2018, 06:51 AM
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#4
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,743
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Jet propulsion systems are a narrow-market product so they tend to be expensive and limited in availability.
I’ve thought of having a less than 15 hp jet unit for years but I think 25-40hp is where they bail out. Like diesel engines. Nobody put them in cars because they wern’t suitable ... until they were. Or are they? Hmm
Of course you could always find/get a water pump remembering that “jets” are just specialized water pumps and rig it up in you’re boat. This would be much much easier to do if you didn’t need it very light. Just any water pump w it’s discharge over the stern would be a “jet” but much sophisticated design and materials is usually necessary. Water-jet propulsion is expensive and inefficient so not the ideal DIY thing
But like me you like thinking out of the box so I’ll be looking for where this goes. One thing will probably be a given and that’s noise. So let the experiment begin.
__________________
Eric
North Western Washington State USA
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10-07-2018, 07:17 AM
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#5
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Enigma
City: Slicker?
Join Date: Oct 2007
Posts: 16,565
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__________________
RTF
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10-07-2018, 07:28 AM
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#6
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TF Site Team
City: Jacksonville
Join Date: Nov 2008
Posts: 11,681
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Quote:
Originally Posted by RT Firefly
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I like the kill switch. Safety first!
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10-07-2018, 07:46 AM
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#7
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Technical Guru
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
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I think the Kawasaki Jet Ski likely has the smallest engine/pump. Noisy, though as exhaust comes out the side of the ski.
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10-07-2018, 08:04 AM
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#8
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Guru
City: South Florida
Join Date: Sep 2014
Posts: 1,088
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The smallest jet drive readily available will be way too much power for a 10' dinghy, and much heavier than a comparable outboard.
For example here's a 9' jet RIB, 90 HP and the whole rig 550lbs. Keep in mind this is an inflatable designed for 90HP, not the same as dropping 90HP into an existing dinghy designed for 10HP
Aqua 9 | Aquascan Ribs
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10-07-2018, 09:09 AM
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#9
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Valued Technical Contributor
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,785
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Taking Ski's advice I checked out Kawasaki's jet skis on line. The smallest has a 1.5 liter, 4 cylinder engine. No way is that going to work with an RIB, it has to weigh 250 lbs.
Neither do I think that the 125 cc powered surfboard will work. Due to the inefficiency of a jet drive you will need more power than the typical 200 cc 9.9 hp outboard if you want to plane. So you will probably need 350 ccs which is typical of 15-20 hp outboards.
A 20 hp Yamaha outboard weighs about 110 lbs, so a jet drive built around the same engine should weigh approximately the same, maybe more.
So are there any 20 hp 350 CC jet skis on the market? In googling this subject I found a 7 hp powered kayak- Tech Specs — Mokai. The engine and pump weighs 50 lbs and is based on a 211 cc engine. But it sure wouldn't plane a 10' RIB.
David
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10-07-2018, 09:13 AM
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#10
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Guru
City: Ingleside-On-The-Bay, Texas
Vessel Name: Papillon
Vessel Model: 1978 Mainship 34 Trawler #95
Join Date: Jan 2018
Posts: 643
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Quote:
Originally Posted by BandB
Also, for your information, SBT carries a huge selection of remanufactured jet ski engines and systems.
Will be interested in seeing how your conversion works as we are strong proponents of jet RIBS.
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Who or what is SBT
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10-07-2018, 09:43 AM
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#11
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Technical Guru
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
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Kawasaki used to make their "stand-up" skis that were much smaller than modern skis. I think they were two cylinder two strokes. Probably not in production anymore, but nowhere near 1.5liter.
Look up old stuff.
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10-07-2018, 09:46 AM
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#12
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Guru
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
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I really want one of these tiny 10’ mini aluminum jet boats. Looks like so much fun!
https://youtu.be/4n3PJqsXHKE
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10-07-2018, 10:03 AM
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#13
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Guru
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,834
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Quote:
Originally Posted by Steve91T
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What could possibly go wrong? Hopefully natural selection which seems inevitable, will be quick.
Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
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10-07-2018, 10:17 AM
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#14
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Guru
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,964
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Why not an outboard like tens of thousands of workhorse dinghies all over the world?
There were jet pump based RIBs built but I think they were all over 10 ft.
__________________
Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
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10-07-2018, 10:35 AM
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#15
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Senior Member
City: Athens, AL
Vessel Name: Always Something!
Vessel Model: Tiara 3700 open
Join Date: Apr 2016
Posts: 110
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In the early 90's there was a 10' Yamaha powered jet "boat" called Jet n Cat. You can google the name to see photos. They worked well but were ahead of their time. I had one of the 2 original Yamaha built units that were imported for market research. The design is heavy, 3 person capable, with storage. They had a removable transom board that allowed for wet or dry operator / passenger area.
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10-07-2018, 11:07 AM
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#16
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Guru
Join Date: Jun 2008
Posts: 5,037
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Quote:
Originally Posted by Keysdisease
The smallest jet drive readily available will be way too much power for a 10' dinghy, and much heavier than a comparable outboard.
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People put built up V-8s in old VW Beetles.
My son put a juiced up Cummins 6BT in a Chevy s-10 pickup.
What about the Hellcat?
There is always the quest for more power.
__________________
Jay Leonard
Ex boats: 1983 40 Albin trunk cabin, 1978 Mainship 34 Model 1
New Port Richey, Fl
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10-07-2018, 11:17 AM
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#17
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Guru
City: Huntersville NC
Vessel Name: Abeona
Vessel Model: Marine Trader 47’ Sundeck
Join Date: Sep 2016
Posts: 898
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Quote:
Originally Posted by jleonard
People put built up V-8s in old VW Beetles.
My son put a juiced up Cummins 6BT in a Chevy s-10 pickup.
What about the Hellcat?
There is always the quest for more power.
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A 6BT in an S10? I have got to see that. I have a 6BT in a 99 F350 and absolutely love it.
I agree, no such thing as too much power.
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10-07-2018, 11:57 AM
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#18
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Senior Member
City: Rapid City, SD heading back to the PNW
Join Date: Oct 2014
Posts: 212
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Bayliner used to make a little jet boat called the JAZZ
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10-07-2018, 12:01 PM
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#19
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Valued Technical Contributor
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,785
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Ski, you are right. Apparently Kawasaki invented the term stand up jet ski and sold them with 300-400 cc engines in the late 70s and 80s. That would be a good choice to find a junker and rebuild the drive to use on a RIB. Will be heavy though.
David
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10-07-2018, 12:02 PM
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#20
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Guru
City: Meydenbauer Bay Yacht Club
Vessel Name: Lulu (Refugio sold)
Join Date: Mar 2012
Posts: 1,284
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I love my WhisperJet, but truly hated a Nautica RibJet I had previously. Squirrelly low speed handling, 1000 rpm just to maneuver, noisy as hell - this is not a good application for that type of propulsion.
__________________
Keith
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