adding a outboard to a double ender help

Discussion in 'Boat Design' started by Bruce Boating, Jul 20, 2019.

  1. Bruce Boating
    Joined: Jul 2019
    Posts: 3
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    Location: South Carolina

    Bruce Boating New Member

    I got myself a 20' fiberglass double ender lifeboat and i have a 50hp outboard i would like to add to it. And i know I don’t need that much power but it is a fourstroke i have sitting around...and i plan on slow boating 10 knots would be nice. Is there a good way to mount a outboard designs out there..????
     
  2. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    I had a smaller motor on a 20 ft double-ender trimaran that was mounted on the side. It had the same problem as double-enders like Wharams had, pushing a wall of water up over the motor at speed even at under ten knots.
    You could get around it by using as long a shaft as possible and putting some sort of fairing in front of it.

    In your case, if you are just content to do slow cruising, just make a bracket hanging over the side, but make sure you incorporate some sort of streamlined protection in the front, and also make it easy to lean on the bracket in case you need to take the motor cover off out at sea, to do any maintenance.

    If you are a bit safety conscious, I would also incorporate some flotation into the fairing, in case the motor stops, and you are sideways into waves. A little bit of lift as the wave approaches the boat could make the situation a bit more pleasant.
     
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    10 knots is unlikely. You could investigate an internal well, depending on what you have to work with.
     

  4. rwatson
    Joined: Aug 2007
    Posts: 5,818
    Likes: 269, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Speed and weight are highly dependant on the dimensions on your 20 footer. I was imagining something with at least a 6foot beam, heavy construction.
    It occurred to me that you might have something much lighter, in which case 50hp is going to be overweight.
     
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