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  1. #1
    Join Date
    May 2001
    Posts
    15,572

    Default Jet drives on a 60’ boat

    I know next to nothing about jet drives. There’s a 60’ Aquastar with them fitted. I guess that’s pretty unusual for a boat of that size. 704hp Cats linked to Hamilton fat drives.

    What are the pros and cons? My guess is less drag therefore a higher speed and/or more efficient. And possibly more manoeuvrable than shafts, not that shafts aren’t manouverable.

    Any other suggestions?

  2. #2
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    5,345

    Default Re: Jet drives on a 60’ boat

    Shallow water .
    There’s maintenance issues underwater hydraulics for steering and the reversing bucket and impeller wear .
    I don’t know what the time interval is for a strip down .

    Ultimately they say less drag , no P bracket or rudder so marginally more efficient fuel wise or faster for a given fuel burn compared to a shaft equivalent.

    Ropes / weed getting sucked in wrapping around is a haul out job not a diver only job .

  3. #3
    Join Date
    May 2001
    Posts
    15,572

    Default Re: Jet drives on a 60’ boat

    Quote Originally Posted by Portofino View Post
    Shallow water .
    There’s maintenance issues underwater hydraulics for steering and the reversing bucket and impeller wear .
    I don’t know what the time interval is for a strip down .

    Ultimately they say less drag , no P bracket or rudder so marginally more efficient fuel wise or faster for a given fuel burn compared to a shaft equivalent.

    Ropes / weed getting sucked in wrapping around is a haul out job not a diver only job .
    I did think shallow water, but then thought the keel would be about as deep as props.

    So just the same as jet ribs, susceptible to rope and weed. There’s lots of it about!

  4. #4
    Join Date
    Jan 2012
    Location
    Reading
    Posts
    572

    Default Re: Jet drives on a 60’ boat

    Quote Originally Posted by longjohnsilver View Post
    I know next to nothing about jet drives. There’s a 60’ Aquastar with them fitted. I guess that’s pretty unusual for a boat of that size. 704hp Cats linked to Hamilton fat drives.

    What are the pros and cons? My guess is less drag therefore a higher speed and/or more efficient. And possibly more manoeuvrable than shafts, not that shafts aren’t manouverable.

    Any other suggestions?
    Here is an even bigger boat on Jet drives
    https://www.boatinternational.com/ya...e-india--87851

  5. #5
    Join Date
    Feb 2012
    Location
    Amersham, Bucks, boat in Lymington
    Posts
    348

    Default Re: Jet drives on a 60’ boat

    And wasn't Azzam built using water jets ??

  6. #6
    Join Date
    May 2001
    Posts
    15,572

    Default Re: Jet drives on a 60’ boat

    Quote Originally Posted by Ian h View Post
    Here is an even bigger boat on Jet drives
    https://www.boatinternational.com/ya...e-india--87851
    11 gallons per mile @ 34kts.

  7. #7
    Join Date
    Dec 2005
    Location
    Live London
    Posts
    3,840

    Default Re: Jet drives on a 60’ boat

    Guy I know has a 115ft azimut on her drives.

    Just a large Williams !

  8. #8
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    4,194

    Default Re: Jet drives on a 60’ boat

    I was under the impression that you needed bigger engines and fuel burn to run jets but like aircraft the water jet gives constant thrust whereas a prop will reach a plateau at WOT and top engine /prop revs. I.e jet is not only able to go faster but also to sit in a favourable torque band at a greater range of speeds when accelerating.

  9. #9
    Join Date
    Apr 2005
    Location
    Long Beach. CA.
    Posts
    2,690

    Default Re: Jet drives on a 60’ boat

    .

  10. #10
    Join Date
    Jan 2013
    Location
    Guernsey
    Posts
    386

    Default Re: Jet drives on a 60’ boat

    One of the Brecqhou boats that runs out of Guernsey is an Aquastar commercial hull running Cummins QSC with Hamilton jet drives.

    After many years of commercial use, the drives now look very tired. If you are thinking of buying a similar set-up, a bloody good engineer's survey is a must. Spare parts may be hard to come by now too.

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