jetski motor in Catamran like a Gemini 105

Discussion in 'Multihulls' started by videorov, Feb 7, 2013.

  1. videorov
    Joined: Dec 2006
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bradenton, Fla

    videorov Junior Member

    That would be cool, kickup the rudders and crankup the keels and then steer
    the boat with the jets in real shallow water.
    If I had the warehouse to build it I would put one together and see how it would work out.
    Wonder if anyone has tried something like that. Would be cool to try it.
     
  2. luff tension
    Joined: Aug 2010
    Posts: 60
    Likes: 5, Points: 8, Legacy Rep: 10
    Location: auckland

    luff tension Junior Member

    This was tried on a cat in NZ, well jet directional drives were and I believe they were abandoned in favour of a conventional diesel/shaft/propeller system.
    It was built by Rob Mulder (Im pretty sure that was his name) in Whangarei and about 60ft, the rest if the details escape me at this stage.
     
  3. cavalier mk2
    Joined: Mar 2010
    Posts: 2,074
    Likes: 39, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    Its not that jet drives don't work, they have been used in multihulls. The problem is the high fuel consumption compared to a prop.
     
  4. Richard Woods
    Joined: Jun 2006
    Posts: 2,161
    Likes: 141, Points: 63, Legacy Rep: 1244
    Location: UK, USA and Canada

    Richard Woods Woods Designs

    IIRC Tony Smith tried them on his Telstar trimaran in the mid 1970's but quickly went back to outboards

    jet drives are inefficient at low speeds. You'd also have to work out what to do with the reverse bucket when sailing

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  5. tomas
    Joined: Nov 2012
    Posts: 281
    Likes: 16, Points: 0, Legacy Rep: 147
    Location: California

    tomas Senior Member

    Richard, what if they were deployed underneath the rockers, instead of at the rear, like 360-degree pods, without buckets?
     
  6. Richard Woods
    Joined: Jun 2006
    Posts: 2,161
    Likes: 141, Points: 63, Legacy Rep: 1244
    Location: UK, USA and Canada

    Richard Woods Woods Designs

    what do you mean by "rocker"?

    rotating the whole engine sounds complicated and heavy

    Richard Woods
     
  7. tomas
    Joined: Nov 2012
    Posts: 281
    Likes: 16, Points: 0, Legacy Rep: 147
    Location: California

    tomas Senior Member

    I haven't seen this on a cat but I was picturing something like what Brian Eiland has shown on his site here:

    http://www.runningtideyachts.com/dynarig/Section_8_and_Rim_Drives.php


    What Brian shows is actually more efficient since it's propeller-based but loses the shallow draft that the OP mentions.

    EDIT: I found Brian's thread about this: Exciting new thruster propulsion
     
  8. Number4

    Number4 Previous Member

    Jet nozzles must be out of the water.
    Jet boat motors work most efficiently at high rpm.
    A 150hp jet ski motor making 30 thrust hp would be running at maybe 60 shaft hp. The OP's Gemini only needs 30hp
    The Molokai jet canoe has a 7hp jet unit, and there are 25hp jet outboards available.
    I doubt they would be anywhere near as efficient as a diesel prop.
     
  9. goodwilltoall
    Joined: Jul 2010
    Posts: 811
    Likes: 20, Points: 18, Legacy Rep: 31
    Location: nation of Ohio

    goodwilltoall Senior Member

    There's an article in one of the recent Woodenboat sister magazines about a lobster boat of about 20' that had jet drive installed in the new build. They had to buy a brand new Kawasaki waverunner - tear it down to the basic engine/jetdrive unit and then put this in for propulsion. Very interesting, maybe kawasaki or another company will start manufacturing an affordable jet drive by itself . Honda has a jet drive outboard.

    Recently had TV installed and saw the end of a show where about 5 guys on seadoo's used them for journeying to remote regions of Alaska. It looked like each one had 10 five gallon jerry cans on the back, they also had to carry provisions and every night set up tents at different locations. Thought about beefing up Fedeli and adapting the kawasaki unit to it for same purpose.
     
  10. videorov
    Joined: Dec 2006
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bradenton, Fla

    videorov Junior Member

    Jetdrives

    They do have jetdrive outboard ebgines I have seen in the past. The
    can put a jetdrive lower unit on a outboard.
    Yes they revup a bit and I guess is some gas.
     

  11. DennisRB
    Joined: Sep 2004
    Posts: 1,265
    Likes: 24, Points: 38, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    Also it will suck rock and sand into it when used in shallow water. Outboards make more sense.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.