Jet ski conversion to sail drive

Discussion in 'Boat Design' started by Forecaddie, Sep 10, 2023.

  1. Forecaddie
    Joined: Apr 2023
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    Location: Brisbane Australia

    Forecaddie Junior Member

    Has anyone converted a jet ski to electric sail drive water craft.
    I want to take an outboard leg and mount the gear box and prop in the hull where the jet drive is located. Would I get cavitation/ poor performance if located there?
    What electric motor brand are people using?
    Of course need to look at batteries too. 48v, 12V?
     
  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Do you have an old jet ski (a Yamaha Waverunner perhaps?) already, perhaps with a non-functioning petrol engine?
    How do you propose to attach the lower section of the outboard leg to the hull of the jet ski?
    And then attach the electric motor to the gearbox - with a sort of 'Z' drive arrangement?
    What speed are you hoping to do with the electric motor - similar speeds to what the existing petrol motor can achieve?
    And what range will you need between recharging your batteries?
     
  3. ChrisVJ
    Joined: Nov 2021
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    Location: Kelowna

    ChrisVJ Junior Member

    Who likes the idea of those bare legs and other parts meeting a spinning prop during an upset? If you really have to go electric why not couple your motor to the jet drive? (Though I think either way you will find the range very, very limited.)
     
  4. seasquirt
    Joined: Dec 2015
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    Location: South Australia

    seasquirt Senior Member

    Hi Forecaddie, I'm a bit confused. What is an electric sail drive water craft. Can you show us a sketch ? Does it have sails or wind power and electric propulsion ? Jetskis need power to plane, meaning a power packed electric system (48V) which is light weight and marinised, which sounds very expensive and a short run time to me. Weight and low power in a PWC means it will be a displacement affair, not fast or stable as they are on the plane with an engine. Maybe a long 3 - 4 seater or more will support all the components you will need to fit in to make it even make way. A ducted or shrouded propeller on your leg may be safe and functional, but definitely not go like a jet. A surface drive prop may work better but be dangerous, as Chris has eluded to above. You will have to remember to lift the leg when beaching, or it will all be very short lived. No skimming over shallow water and reefs and weeds.
     
  5. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Saildrives do not lift. They would be sticking out about 18 inches (46 cm).
     
  6. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Jet ski hulls are made for speed, and do not like to go slow, as I fear you will be doing a lot of with limited electric power.
    Most of them wander terribly at slow speeds as well, an that will likely get worse when overloaded with batteries.
     
  7. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Have a stand up jet ski, so not an apples to apples comparison. My superjet had about 75 hp and weights 305 lbds according to the spec sheet. I'm trying to think of an outboard or sail leg that has even half that power to weight ratio. The boats not really stable when not under power... a lot of power. The ocean skis are far more stable at rest but still do best in motion, and are power intensive monsters.

    Adding weight and decreasing power seems like a tough way to improve them.

    Would think there would be more suitable options for a battery propelled watercraft. Something that planes at a lower speed.

    Granted some of these high rpm small electric motors can put out some crazy numbers. Wonder what kind of battery pack it would take to equal the 3+ gallon tank on my little superjet. Touring around a meandering river it lasts a while, but jumping in the surf it goes way to fast.
     

  8. portacruise
    Joined: Jun 2009
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    Location: USA

    portacruise Senior Member

    Using hydrofoils might help, but it is unlikely to equal the performance of a petrol jet ski, while adding some downside associated with foils. There's probably some good reasons that IC powered jet skis don't use them..
     
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