Inboard Conversion to Outboard

Discussion in 'Boat Design' started by Nordski, Aug 13, 2020.

  1. Nordski
    Joined: Feb 2019
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    Nordski Junior Member

    Considering converting this design to outboard power......any thoughts?
    Screen Shot 2020-08-13 at 7.24.55 PM.png
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Is there any particular reason you want that boat, rather than one already designed for an outboard ?
     
  3. Nordski
    Joined: Feb 2019
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    Nordski Junior Member

    This is a 24' Garvey......I haven't come across a design like this other than a planing hull.......I would like to find a displacement design with outboard power if available.
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    What design is she?
    Would you have single or twin outboards, and how much power are you thinking of?
    Would you keep the keel / skeg as shown?
    She appears to be about 23' LOA - might be easier to just get a set of plans for a proven garvey type boat?
    Such as this one from the Wooden Boat Store, and lengthen her a bit?
    19' Garvey, BIG BEN https://www.woodenboatstore.com/collections/powerboat-plans/products/19-garvey-big-ben
    Or a stretched version of this garvey from Glen-L?
    outboard motor garvey hull boat plans https://www.glen-l.com/designs/outboard/jimbo.html
     
  5. Nordski
    Joined: Feb 2019
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    Nordski Junior Member

    The design is Atkin's "Barnegat"......23'.............would be single 20hp outboard........keel and skeg would not be included............some weight forward would likely be needed............will have a cuddy cabin forward...........
     
  6. bajansailor
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    bajansailor Marine Surveyor

    But surely the garvey in your example Nordski would essentially be a planing garvey if you remove the keel, when you take into account all that flat planing surface?
    Have you seen the Spira garveys?
    Spira International Inc - Puchie Special Garvey Dory Plans https://spirainternational.com/hp_puch.php
     
  7. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    That keel is gonna cause some troubles. No dimensions, but the keel looks like it would cause some disturbances for the incoming prop water. And not sure how it is helping protect a prop that is 12" higher than it..
     
  8. Nordski
    Joined: Feb 2019
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    Nordski Junior Member

    Not sure that the design I posted would be consider a planing design due to the shape of the bottom......I could be wrong........I have built one of the Spira Garvey's....... "Avila" shown not his web site is my boat. I'm looking for something just a bit different than what Spira has.
     
  9. Nordski
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    Nordski Junior Member

    The keel would not be build as shown.......just and external small keel 3/4" x 6" would be built......1 bottom strake on either side of the keel 3/4" x 4" would be installed. Bottom would essentially be flat aft.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    You could go to outboard easily enough, the problem would be deciding what height to mount it, too high and you could find ventilation problems when the boat pitches, too deep and you will get a lot of drag, and a fountain, from the drive leg. The skeg could be cut back substantially, to leave a vestigial one that supplies a little bit of lateral plane aft, but tapered so as not to interfere with the outboard.
     
  11. Nordski
    Joined: Feb 2019
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    Nordski Junior Member

    The 2ohp Honda engine mount has several holes (4...I believe)........I could build the transom so that the engine would mount in the second hole with the cavitation plate 2" below the bottom of the hull. I could then move the engine up or down about 1" from there without the need to modify the transom.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't think that is going to be enough, have you already got a 20hp Honda ? If so, what is the drive leg looking like, above the cavitation plate ? What is it, L/shaft ?
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd say it is a job for an extra long leg, high-thrust variant OB. These typically are streamlined enough for a distance above the cav plate, so they can stand being a little deeper beneath the boat.
     
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  14. Nordski
    Joined: Feb 2019
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    Nordski Junior Member

    Yes.........I acquired a new 20hp Honda long shaft........The "Redwing" series of plywood flat bottom boats seem to have good reviews from builders and they use a small outboard............wouldn't the performance be similar to what I am proposing?
    Screen Shot 2020-08-14 at 3.20.23 AM.png
     

  15. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    It is a planing hull with the keel. It's designed to do 15 mph with a 35hp inboard . The boat is designed for an engine weight up to 600 lbs so it would ride high with an outboard.
     
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