Outboard Placement on Sailing Dinghy

Discussion in 'Boat Design' started by Kayaker, Aug 4, 2021.

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  1. Kayaker
    Joined: Aug 2021
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    Location: Town of Bremen, ME, USA

    Kayaker New Member

    I'm installing a 2.5hp Suzuki on an old Eli Scout sailing dinghy, not meant for this function. As the image shows, the skeg extends about 4" below the transom. Hanging the motor centered on the boat places the (anti)cavitation plate below the hull and about 2/3 of the way down the skeg. The propeller arc would overlap the skeg by about 3/4", about 8" back from the transom. I assume the speed with motor would be 5 knots or so; so my question is whether the skeg is likely to induce ventilation if the motor were operated in the configuration as shown. My alternate plan is to mount it off center, but that would involve more modifications than I would like. Any informed opinions will be welcome.
     

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  2. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    Not a problem with that low horsepower.
     
  3. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Ahhh.... You know you can roll propel or scull it faster in those few time you need to go upwind? Just saying...
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Should be OK
     
  5. Ike
    Joined: Apr 2006
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    Ike Senior Member

    I have a similar situation with my 12 foot dinghy (not a sailing dinghy) the 2.5 Suzuki hangs at about the same position as on your boat. Doesn't affect it at all. And yes I can probably row it faster than the O/B, but I'm old and tired of rowing.
     
  6. Kayaker
    Joined: Aug 2021
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    Location: Town of Bremen, ME, USA

    Kayaker New Member

    And I want to go further than I can row, esp. with my wife in the boat.
     
  7. messabout
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    messabout Senior Member

    I seldom have the audacity to disagree with Jehardiman. In this case, I say, no way in hell that you could scull faster than the 2.5 hp outboard would drive the boat.

    If the boat is beastly heavy, the outboard would have to work pretty hard. In the same heavy boat, sculling or rowing would not be as fast. Humans are not capable of producing as much output power as that little engine can.

    The easy way to resolve Kayaker's question is to hang the engine on the boat and give it a try.
     
  8. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Just fill the space between the skeg and the leg with a chunk of something. A bit of pool noodle Bondoed to the skeg so the leg lands on it will fix any possible problem. You can hear the ventilation at this scale. The prop looks like it came off a 6 hp. It won't need to do much more than idle. I ran a 2.5 propped with a six on a 21', 1600lb canoe and it would run for a week on 6 gallons of gas.
     

  9. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    I doubt that. I know I could maneuver my Ranger 26 (Mull) sailboat anywhere I wanted to without lowering the 9.9 Honda 4-stroke unless I wanted to go dead upwind for hours. Sailboats have easily driven hulls, just need to work them like they did 100 years ago. Remember, "hull speed" is all about available power, not actual speed through the water. You would be surprised how little the speed difference is between 0.75 ehp and 1.5 ehp (i.e. 0.6 * 2.5 shp) really is.
     
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