Boat Idea for Inboard Detroil Diesel 3-71 100 HP

Discussion in 'Boat Design' started by Manuel R Alonso, Jun 9, 2021 at 8:13 AM.

  1. Manuel R Alonso
    Joined: Wednesday
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    Location: 33332

    Manuel R Alonso New Member

    Looking for ideas for s simple open deck boat that would work with a 100 hp 1500# inboard detroit diesel and plane 25-30 MPH? Open to aluminum or wood / fiberglass construction. Any ideas? Basically trying to figure what might work to acomplish that with this engine.
     
  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Manuel.
    Are you looking to buy a suitable second hand boat that would be a good match for your engine, or are you planning on building a boat from a set of plans?

    If a second hand boat, would a vessel like a Shamrock appeal?
    1995 Shamrock 220 Stalker Center Console for sale - YachtWorld https://www.yachtworld.com/boats/1995/shamrock-220-stalker-3817956/

    I think that she would be hard pressed though to achieve 25 - 30 mph with a 100 hp diesel.

    If you are looking to build a boat, would something like a dory be suitable?
    There are a variety of them shown here -
    Spira Boats - Wood Boat Plans, Wooden Boat Plans https://spirainternational.com/hp_wood_boats.html
     
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  3. Manuel R Alonso
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    Location: 33332

    Manuel R Alonso New Member

    Want to build, already had a 26 open shamrock that I put a 370 cummins in it. Was not a success, although I love the shamrocks and the keel, the prop is too small which I belive hurts them in efficiency.

    The dory's look nice and simple, but that flat bottom may be a little rough, although efficient for acheiving my desired speed with a heavy 100hp diesel.

    Thanks
     
  4. Manuel R Alonso
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    Manuel R Alonso New Member

    Have a 23-3 formula in the back yard also that needs to be redone, but dont think 100 hp will move it with its aggressive deep vee
     
  5. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    Why not blow out the Shamrocks prop tunnel to fit a bigger prop?
    A Cummins 370 with about an 19” prop should be real nice in there.
    I did just that a few years back, it worked really well.
    I’ll provide details, if you’re interested?
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    100 hp would not drive a 3000 lb boat to a 25-30mph cruise speed, which is realistically about the minimum weight you could hope for, starting with 1500 lbs of engine, using the best lightweight construction methods. low 20's mph might be possible with careful hull selection, the fact you want a stripped-out open boat gives you some hope.
     
  7. comfisherman
    Joined: Apr 2009
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    comfisherman Senior Member

    371..... maybe a giant muffler that looks like a boat.

    371 was a decent but noisy gen engine but that's a heavy 100hp engine. Good at converting diesel to noise.

    Maybe a ply skiff with a decent beam would plane to 25 and help spread the weight?
     
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  8. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Yes, the noise factor is an obstacle
     

  9. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    One of our local fishermen runs a 371, and has acquired the nickname “Machine Gun Kelly”!
     
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