twin outboards on 12ftx40ft barge

Discussion in 'Boat Design' started by brunsco, Sep 5, 2011.

  1. brunsco
    Joined: Sep 2011
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    Location: holden beach nc

    brunsco New Member

    I have purchased a 12ftx40ft steel barge and want to mount twins outboards. The stern is square with a raked bow. The previous owner used a push boat. I have seen a barge with twin 60's that worked well. My question is the mounting bracket design and distance between the motors. Any help would be appreciated. We are in Southeastern NC.
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If you want good maneuverability, then mount the engines towards the outboard corners of the barge. If you're not going to run slalom races with this puppy, then they can be mounted on the center line with at least 24" between them.

    The wide engine spacing assumes you'll use the engines as true twins, reversing one or playing with throttle settings to help with maneuvering.
     
  3. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    I'm betting the twin 60's you saw were high thrust motors. Thats the upper HP I have seen for High Thrust in the Yamaha line, and a 4 cycle too. For pushing a barge high thrust is what you want.

    The same 60 HP standard O/B will turn a smaller prop faster, High Thrust O/B turns a larger prop slower providing more thrust from the same HP.

    http://www.yamaha-motor.com/outboard/products/subcathome/4/home.aspx

    The 4 cycle makes it quieter, more reliable and uses plain gas without oil saving $$

    Steve
     
  4. Chase_B
    Joined: Aug 2011
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    Chase_B Junior Member

    I have a high thrust 4 hp on the back of my 12' by 6' pontoon ,..it pushes my boat along very well,.. I agree high thrust can do better with a lower hp,.. it's like having a granny gear in a big truck
     

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  5. brunsco
    Joined: Sep 2011
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    brunsco New Member

    The motor set up I saw was High Thrust Yamaha's. They were mounted close together. I want the twin set up for manuveability. My thought was that the wider apart the better turning radius I would achieve. I have operated twins but not familiar with setting up twins. How far apart can the steering linkage reach without issues or is that not a factor? I am thinking approx. 6ft center to center. That would keep the motors 3ft from side to centerline of motors or 2ft from edge of motor. How do I calculate the mounting bracket height?
     
  6. CatBuilder

    CatBuilder Previous Member

    The info you need is right here:

    http://www.yamaha-motor.com/outboard/products/subcatspecs/4/specs.aspx

    (shaft length)
     
  7. keysdisease
    Joined: Mar 2006
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    keysdisease Senior Member

    Even High Thrust outboards don't pull worth a damn in reverse, but for turning a wider set would be better. You don't have to use a tie bar, there are hydraulic tie bars that work just fine and simplify stuff at the stern.

    http://www.jamestowndistributors.co...raulic Steering - Catamaran Pontoon Outboards

    These were developed for catamarans and pontoon boats, will simplify things.

    Conservative typical setup for outboards is cavitation plate level with the bottom.

    Steve


     
  8. Submarine Tom

    Submarine Tom Previous Member

    When I had twins on my 25 X 10 foot houseboat I had them on six foot centres because that's where the skeggs were. It worked great but I prefer the single in the centre.

    -Tom
     
  9. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    40 feet is a substantial length to be using 20" leg outboards. To avoid having the props leave the water when it pitches, they will need to be reasonably well immersed, which then creates the possibility of getting water into the powerheads. Depends on the likely operating conditions I guess, but worth consideration.
     

  10. brunsco
    Joined: Sep 2011
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    brunsco New Member

    Thanks for all the help. I had not considered the pitch in a turn. I have worked on a similar barge with twins mounted close together and did not notice any listing in a turn. I would estimate a max. list of 3 inches in the worst of conditions. So many variables due to weight changes from day to day. We will have delivery on thursday morning. Thanks again.
     
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