transom height

Discussion in 'Boat Yard Basics' started by levip, Dec 15, 2010.

  1. levip

    levip I Love microskiff.com!

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    ok so im redoing my transom, i measured the height from the bottom of the boat to the top of the fiberglass and its exactly 15" vertically the motor ill be using is a 15" shaft 1956 5.5 evinrude
    my question is can i cheat the engine up and inch or so with the new plywood thats going in to reduce drag OR will that cause the prop to cavitate
    i read some where that the cavitation plate should be 1 inch above the lowest part of the hull for maximum efficiency and the least amount of drag but with a 5.5 will it make that big of a difference????? im not trying to break any water speed records just looking for maximum efficiency without worrying if ill blow the prop out in a sharp turn

    any help on this matter is greatly appreciated
    levi
     
  2. firecat1981

    firecat1981 BBA Counselor

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    Alot of it depends on the type of hull, and really it's not an exact science. What you can do is cut the transom higher, say 16.5", and try it, if it vents when running then cut 1/4" and test again until you are happy. Worst case is you end up cutting it all the way back to 15".
     

  3. levip

    levip I Love microskiff.com!

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    its a 13' gheenoe highsider
    i dont really want to have any exposed wood though?
    would i just test it before i wrapped the fiberglass over the top of the transom?
     
  4. firecat1981

    firecat1981 BBA Counselor

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    you could, glass it in as you would and seal the top with some of the epoxy to keep the water out, once you find a height you like then finish the job as soon as possible.
     
  5. Brett

    Brett > PRO STAFF <

    Leave the transom height as is, reinforce it and glass it.
    Then hang the 5.5 hp outboard on there and go fishing.
    The props available for the 5.5 won't let you run near the surface.
    I tested this extensively on the Grass Slipper.
    A custom prop will cost more than the outboard is worth.
    The difference in speed will be less than 1/2 mph,
    not worth the effort or expense.
    Spend your time and money on the water,
    not trying to turn a utility hull into a racer.

        
     
  6. firecat1981

    firecat1981 BBA Counselor

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    Brett? against tinkering? is that you? did your wife hack your account again? ;)
     
  7. mark_gardner

    mark_gardner I Love microskiff.com!

    i agree with brett ;) fix your transom, hang your motor and go fishing :cool:
     
  8. levip

    levip I Love microskiff.com!

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    yeah thats what i was thinking thanks guys
    jnow i just gotta wait till it warms up a bit in my garage or the fiberglass wont set up its been highs in the 40s and lows in the 20 for 2 weeks now
     
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