Light, small, speedboat for 40HP Nissan outboard

Discussion in 'Powerboats' started by Maciek188, Mar 17, 2016.

  1. Maciek188
    Joined: Jul 2005
    Posts: 10
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    Location: Brooklyn, NY

    Maciek188 Junior Member

    Hi All,
    Would like to design/build small, fast speedboat powered by my 2 strokes, 40 HP Nissan NS 40C outboard. Weight of the engine is 128 lb. Should be 2 seats, plywood and fiberglass construction, as light and small as possible, for 2 people, 135 lb each. What would be the best size and shape to reach maximum speed on calm water? Also would like to hear some advice on propeller for this engine. Originally it came with 10-1/2" by 11' pitch. What propeller should I use and what would be expected speed? 10" by 19"? Have big garage with many power woodworking tools and knowledge how to use them so not afraid to do the job. Any advice would be highly appreciated.
    Last edited: Mar 18, 2016
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    You will find plenty of plans for such a boat on the net, but you need to specify what you want out of it. If the plan is a runabout for two people, with maximizing speed the aim, it probably isn't ideal to be building around a 40hp engine. You might get 30 knots max, but it will be a light boat with little load carrying capacity. You will likely be able to find a coarse pitch prop for it, but find planing the boat with it a strain unless weight is strictly controlled. And if you have to slow down in curly water, an unsuitable match to the task.
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Agreed, there are plenty of designs that can handle a 40 HP outboard, but you do need to further define your goals, so the design selection process can narrow the offerings.

  4. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    I built this boat in 1958 when I took wood shop my Junior year of High school. first time in the water with 4 people 2 friends @ 160 pounds each, my Dad @ 270 and myself @ 125 with a 35 HP even-rude it came right up on plane and went close to 30 mph no gauge.
    Used heavy mohogane for frames so using DF would make it lighter. I would thicken the transom with a + layer of 1/2" ply for 40 HP.
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