Prop Pitch on 50HP Johnson 21ft Carolina Skiff

Discussion in 'Outboards' started by byob1985, Mar 13, 2014.

  1. byob1985
    Joined: Apr 2013
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    Location: Chesapeake Bay

    byob1985 Junior Member

    Hey Experts,

    Looking for the ideal prop pitch for my set-up. 1988 21ft. Carolina Skiff (8ft. wide at top of gunnel) w/~2000 50HP Johnson 2cyl. Outboard (13 spline, I think).

    Current prop is 13 x 11. New config on boat will be custom commercial work platform and add ~750lbs of weight to the boat. Run a 12 gallon fuel tank, single battery and operate mostly solo (I weigh ~150lbs). Will occasionally add another ~500lbs+ in gear/product.

    Thinking I need to drop an inch in pitch to maybe 13 X 10, but seeking advice from those with more experience. Don't care about speed too much, as I only have a 50HP to begin with. More concerned about ability to plane and cruise with that much added weight.
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    If you have a tachometer, check what your full throttle rpm figure is. Then compare that with the maker's recommended rpm range. (4500-5500 ??) If it is at the bottom end, or lower, you need to go down in pitch, although I doubt there is a lot of room to go much further down in pitch than 11" . At a rough guess, I'd say you would be doing no more than 15 knots flat-out, is that about right ?
     
  3. byob1985
    Joined: Apr 2013
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    Location: Chesapeake Bay

    byob1985 Junior Member

    I actually don't have a tach. If I had to guess w/the 13 X 11, I'm probably actually running somewhere between 17-20 knots, best guess.

    I have had 6-7 people in the boat (~900lbs) and it seemed to hop up on plane and cruise fine. So maybe don't go down an inch on pitch? Looks like 10 is close to smallest; seen some 12 X 8/9 props for outboards around my size.
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Have you got much throttle left at your cruise speed ? You will be using a lot of fuel if you don't.
     
  5. byob1985
    Joined: Apr 2013
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    Location: Chesapeake Bay

    byob1985 Junior Member

    Yea, I would say I have about 1/4 throttle left once I get on plan and am cruising. Not a ton, but enough to increase speed.
     

  6. boatbuilder41
    Joined: Feb 2013
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    Location: panama city florida

    boatbuilder41 Senior Member

    Keep the 11 pitch. The two cylinder 50,55, 60 HP omc engines had a long stroke with a low wrist pin location in the piston. This made the rod angle increase. If you are wondering what hat the inside of one looks like...... Then just over rev one for a few hours. We used to run them in well skiffs commercial fishing. With the motor in the bow made them more subject to cavitations... Which led to excessive rpm. These motors couldnt take excessive rpm.
     
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