Reversing output full time

Discussion in 'Inboards' started by DogCavalry, Jul 24, 2021.

  1. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    I'm aware of the limitations of velvet drives re input output. If I install a pair of RH engines, is it possible to install a marine transmission that reverses one output for continuous duty? Is that even a thing?
     
  2. fallguy
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    fallguy Senior Member

    It'd be news to me.
     
  3. bajansailor
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    bajansailor Marine Surveyor

    Are you looking to have a pair of handed propellers, with one RH and one LH?
    If they were both RH or LH would that matter hugely?
    I know that there would be a net heeling moment, but would it be significant enough?
     
  4. gonzo
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    gonzo Senior Member

    Volvo transmissions can run with left or right handed output and I believe ZF also has some models that do.
     
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  5. fallguy
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    fallguy Senior Member

    Hang some ob off the back. Faster and easier to do for diy. No bilge blowing requirements and all the jazz.

    maybe long term io is better, but I'd jackplate OBs

    why would a workboat want to gobble up all the deckspace for double motor boxes?

    Sorry, but not a fan of the io here.
     
  6. gonzo
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    gonzo Senior Member

    Depending on what work the boat does, outboards may get in the way. For example, it would make it impossible to drag nets up the stern.
     
  7. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people


    Yes, the notion is a pair of handed props, LH&RH, without also reversing the rotation of one engine. I'm not determined to do this, just exploring options. Does the equipment exist for this? It seems a logical approach, but maybe not. @gonzo pointed out a while back that an engine creates a heeling motion when it speeds up or slows down, and there are gyroscopic effects in normal operation. In a light boat with powerful engines these could make it unmanageable under extreme performance conditions. But for a slower heavier boat the maneuverability with opposite props is good, and both RH engines won't flip the boat at 25 knots.
     
    Last edited: Jul 26, 2021
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  8. fallguy
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    fallguy Senior Member

    he is a cabin carpenter; the motorboxes are in the way
     
  9. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    I will almost certainly install an outboard, but that doesn't prevent curiosity, and it's good to discuss options.
     
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  10. BlueBell
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    BlueBell . . . . .

    (Thread drift warning)

    For me, one of the major benefits of O/B's on a work boat around here is the beach-ability it affords.
    I guess the same could be said for I/O's but I have little workboat experience with them.

    The kick-up ability built in to some O/B's is another big plus around here given the sheer volume of deadheads.
    I don't know if I/O's employ the same shock absorption system.
     
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  11. bajansailor
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    bajansailor Marine Surveyor

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  12. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    I've always been impressed that an outboard could kick up fast enough to matter, when passing over a log at 30 knots.
     
  13. BlueBell
    Joined: May 2017
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    BlueBell . . . . .

    They are fancy systems but it's not hard to exceed the limit and rip them right off the boat.
    Fortunately, I don't speak from experience, but I've seen the results in the boatyard.
     
  14. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Well, the way I've built Serenity, it could literally tear the entire transom off and she wouldn't sink.
     

  15. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    Some Velvet drives are reversible, most other brands definitely are.
    Look for a manual for your transmissions model, it should explain the procedure, the pump must be indexed correctly, and cooling hoses may have to be re-routed.
     
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