Twin outboards. Same rotation

Discussion in 'Outboards' started by Charles Reaves, Jul 25, 2018.

  1. Charles Reaves
    Joined: Jul 2018
    Posts: 7
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    Location: Uk

    Charles Reaves Junior Member

    hi from the uk.

    I am having to Repower my 21ft 1994 Boston whaler outrage. She had twin 130 2 strokes counter rotating. However with a 700lb transom weight limit the best option I can find are Suzuki 100hp but these are not available in counter rotation. My engineer says this is not a problem on this boat. But is it? What should I expect? The boat tilting? The steering always pulling to one side so tiring to helm. Marked difference in turning to one side than the other? Or all somminimal as my to be noticed. Thanks in advance.

    Charles
     
  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell "Whatever..."

    You will get used to the difference quickly, no big deal.
    It's pretty subtle.
    But why not save weight and money and go with a single 200?
     
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    I am not that familiar with the boat, but it is more a vee-hull than a cathedral, from my observations, does it bank heavily in hard turns ? If so, the torque effect may cause a tilt to the left, that you have not previously experienced with the boat. If the helm position is to the right, one-up it may be cancelled out, or some subtle shifting of weights may be enough to level the boat. As to the steering pulling to one side, that can be modified by altering trim settings, and/ or the steering tab on the outboard legs. You will note CR paired engines often have no tab. Hydraulic steering would eliminate that feedback issue completely. If the torque effect is an issue, fitting trim tabs would be an option, but 2 x 100's probably aren't going to have a huge effect on the boat.
     
  4. Charles Reaves
    Joined: Jul 2018
    Posts: 7
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    Location: Uk

    Charles Reaves Junior Member

    Thank you both, that has been very helpful in quieting my concerns.

    My reason for twins include growing up with outboards that were not as reliable as todays models - old anxieties die hard, and having been very grateful on three occasions now over the years in different boats to have had twin engines when one has failed for vastly different reasons and been able to get home.
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    If you have a small torque effect, even with closely spaced twins, differential engine trim might be enough to control it. I don't think you will get into any trouble here.
     
  6. BlueBell
    Joined: May 2017
    Posts: 1,613
    Likes: 420, Points: 83
    Location: Victoria BC Canada

    BlueBell "Whatever..."

    Twin, single, personal choice, I understand.

    The only place I really noticed a lack of counter rotating props was on a Mark 5 Zodiac.
    It had twin 115's and on take off, a full 1/4 turn of the wheel counter acted the torque effect
    of the props and kept the boat straight through the air.
    That was at RHIOT (Rigid Hull Inflatable Operator Training) school in Bamfield BC.
    All the other rescue Zodiacs I've driven were CR and flew straight with no counter steering.
    If you are buying new, I would really consider a single.

    Boston Whalers are fun boats but man do they have some attitude when over powered...
     
  7. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Another option to never disconsider is a smaller reserve engine. So you run a 200 say and back it up with a 25 that has its own fuel and start battery or pull. I get running the two, but if you are fishing the 25 might be a great one for trolling as well.
     

  8. IronPrice
    Joined: Jul 2017
    Posts: 154
    Likes: 7, Points: 18
    Location: NZ

    IronPrice Senior Member

    I have twin 70s with the same rotation on my boat. I have only noticed torque effects when driving onto the trailer. On the water, no issues at all.
     
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