small jet ski engine?

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
jimisbell

jimisbell

Guru
Joined
Jan 13, 2018
Messages
643
Location
USA
Vessel Name
Papillon
Vessel Make
1978 Mainship 34 Trawler #95
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.
 
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.
 
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.
 
6.5_LT_3-762x456.jpg



6.5 HP VANGUARD INTEK Pro LONGTAIL - GO-DEVIL Manufacturers
 
I think the Kawasaki Jet Ski likely has the smallest engine/pump. Noisy, though as exhaust comes out the side of the ski.
 
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

:socool:
 
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
 
BandB said:
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.
Click to expand...


Who or what is SBT
 
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.
 
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.
 
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.
 
Keysdisease said:
The smallest jet drive readily available will be way too much power for a 10' dinghy, and much heavier than a comparable outboard.
Click to expand...

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.
 
jleonard said:
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.
Click to expand...

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.
 
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
 
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.
 
The small stand up jet skis had two stroke motors of 300cc, 440cc and 550cc. The smallest one would be suitable for your intention.
 
This is nuts. OP said nothing about planing. What’s all this talk of 90hp?

But re jimisbell’s post he may have had 90hp in mind.
Seems nuts to me but I’m the low power “nut”.

jimisbell talks of carrying two people and some groceries. That could be easily done w 2hp.
 
Last edited:
Nomad Willy said:
This is nuts. OP said nothing about planing. What’s all this talk of 90hp?

But re jimisbell’s post he may have had 90hp in mind.
Seems nuts to me but I’m the low power “nut”.

jimisbell talks of carrying two people and some groceries. That could be easily done w 2hp.
Click to expand...

He asked what was the smallest jet ski engine...that’s where the 90 hp talk came from.
 
djmarchand said:
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
Click to expand...


Specs from Surfjet link above....
Engine brand Hison
Engine Type 4 Stroke
Engine Displacement 125CC
Max Horse power 20HP
Max speed 40km(24.9mile)/hour
Compression Ratio 10.0 : 1
Recommended Fuel >= 93#
Engine Oil Tank 2.5L
Fuel Tank Capacity 10L
Fuel Consumption 3L/Hour
Passengers 1
Length 2.5m
Width 0.6m
Height 0.3m
Dry Weight 60kg
 
High Wire said:
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.
Click to expand...

One of the Ribjet we had was the Sea Doo explorer but it was about 13' long as you say. Outboards much easier, efficient, better mpg, controllable, common parts, easy to clean a fouled prop, etc.
 
smitty477 said:
Specs from Surfjet link above....
Engine brand Hison
Engine Type 4 Stroke
Engine Displacement 125CC
Max Horse power 20HP
Max speed 40km(24.9mile)/hour
Compression Ratio 10.0 : 1
Recommended Fuel >= 93#
Engine Oil Tank 2.5L
Fuel Tank Capacity 10L
Fuel Consumption 3L/Hour
Passengers 1
Length 2.5m
Width 0.6m
Height 0.3m
Dry Weight 60kg
Click to expand...


At 330 CC you can get 45 Hp bit I think its too heavy...
https://www.powerski.com/faq.html
 
Steve91T said:
He asked what was the smallest jet ski engine...that’s where the 90 hp talk came from.
Click to expand...

OK my bad. That was my oversight.
I’d like to hear from jimisbell and see what kind of boat he has.

I now know he is building a rowboat. That would assumably be FD so only a very small amount of power will be required.
 
Last edited:
I have a customer with a turbine in a Mini Cooper, but he's a crazy 20 something year old gear head.
Jim is I believe in his 70's and looking for something "light" to push a 10' dinghy with 2 peeps and groceries.
I don't think he fits the Chevy 454 in the Nova profile.

:socool:


jleonard said:
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.
Click to expand...
 
You must log in or register to reply here.

Similar threads

HeadedToTexas
Jet ski trailer for RIB?
Replies
12
Views
1K
koliver
koliver
M
Dinghy weight on deck over stern sundeck
Replies
1
Views
362
sunchaser
S
S
Need advice for appliances, gas or electric, if you had a choice
2 3
Replies
61
Views
4K
sndog
S
mvweebles
5-mos Cruising Pacific Mexico Q&A
Replies
11
Views
1K
PNW
PNW
J
Trailerable Trawler List
2
Replies
56
Views
6K
Jbo_c
J

Latest posts

Back
Top Bottom