Oddball non-boat Outboard question

Discussion in 'Outboards' started by Dieboat, Aug 19, 2016.

  1. Dieboat
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    Dieboat Junior Member

    Good day,

    I could not locate a "non boating" question forum and outboards seemed the closest.
    As this website is brimming with DIYers, I am hopeful for indulgence from fellow individualists who push the bounds.

    My thought is to utilize the ring and pinon gears of a 100+ horsepower outboard in the differential of a small (under 50 horsepower) land based vehicle.

    Ideally, I need a 1:1 differential capable of sustaining 1000-1200 rpms, in rough conditions and is bulletproof reliable. Industrial gearboxes, that meet those requirements are very heavy (35-50lbs); automotive gear sets that meet those requirements, are very expensive (thousands).

    I have the ability to machine, but machining custom gear sets from blocks of steel exceeds my skill. Cutting new tines on a pinion shaft or creating an adapter backplate does not.

    Websearching brought me to boat gear sets and DIY custom boat design brought me here.

    The most important questions are: Has this ever been done and if so, who? when? where?

    More hope, that the answers to the aforementioned will define the realities of this idea.

    Thank you for your time
     
  2. gonzo
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    gonzo Senior Member

    You didn't find a non-boat place because we strive to keep non-boat posts out of this forum. There are other forums for land vehicles.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    It would be helpful if you better described what you're trying to do. Finding a 1:1 gear set for an outboard will be a bit of a challenge.

    To directly answer your question, I've never heard of someone putting an outboard's gear set in an automotive rear, nor can I see any advantage to this. Small, angle changing gear boxes are available and often seen on PTO's with ATV's, garden tractors, etc.
     
  4. Dieboat
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    Dieboat Junior Member

    alone

    Forums for land based vehicles utilizing outboard gear sets in differentials?

    Please do not keep the information secret, post it and strive away.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    As PAR says, 1:1 is not going to be available, you'd be lucky to find much less than a 2:1 reduction in that size, and I have no clear idea of what the plan really is.
     
  6. Dieboat
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    Dieboat Junior Member

    Par

    Hello Par,
    It might be sterndrive. I have located Mercruiser gearsets that are 1.47 that look adaptable, but I have not seen one in person. (The local Boat repair and service shop "strives" to ignore non boat questions)

    I am weighing the pro's and con's of different alternatives.
    The only true "automotive" differentials in 1:1 are quick change units that are thousands and out of budget.

    There are PTOs and gearboxes that are 1:1, but they are heavy, will need an oil cooler of some sort and will be difficult to turn.(no differential carrier)

    ATV differentials have merit, but I have yet to find one rated at the proper horsepower and torque in a 1:1 ratio. The longevity ATV differentials in continued (daily) high rpm use causes some concern, but for a rated differential (like off a Can-am or RZR 1000) with the right ratio, I would risk it.

    It was copious googling that found boat gears of low ratio in ring and pinion style.
    I see potential advantages as follows: used "incomplete" sets (1 ring and 1 pinion) can be found for a couple hundred. Some of the gears I have found are from 100 or more horsepower high torque boats, the jarring and force they are made to withstand is impressive.

    I see potential disadvantages as follows: Unsure if a suitable marine ring and pinion exists. I have found some that are "true" ring gears and if I understand the measurements they are 5in in diameter, thereby having a center hole of 3.5in. There is a lawn tractor differential carrier that is 3.5in. Still, it would be nice to find a bigger marine ring gear and a bigger one in 1:1.

    Potential disadvantage 2: Is there a backing plate attached to a marine ring gear? If so, how does it attach? This could have been answered in the local boat shop but, (see strive above)

    Potential disadvantage 3: If I find a ring and pinion and modify it to fit in a differential, will it be possible to correctly shim the gears for operation?

    So, all my potential disadvantages could be confirmed or dismissed in much less time then it took to type this treatise, by someone with an open mind and a knowledge of boat gears or someone with a half open mind and a boat gearset I could take caliper measurements and/or spin in my hands for a few minutes.

    Finally, I am wary about spending time explaining my project. It derails the thread into defending and justifying decisions. In a nutshell, I am constructing a hydraulic hybrid on a budget. Hydraulic motors with the largest efficient torque band are found in low (slow) displacement, hence the need for a 1:1 ratio.

    To end this novella with another question: The complete gearsets show two ring gears with pinion in the middle. It appears that one ring is for forward and one for reverse--is that right? The ads for those gearsets have 2 ratios listed like "1.47, .51" Is one ratio for one ring and the other for the other?
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Outboard and sterndrive gearcases are designed to accomodate thrust loads along the axis of the shaft, not great loads perpendicular to it, so consider that.
     
  8. Dieboat
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    Dieboat Junior Member

  9. Dieboat
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    Dieboat Junior Member

    Trying again

    [​IMG]
     
  10. Dieboat
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    Dieboat Junior Member

    The pictured are a 21 tooth and a 19 tooth gear set from an OMC unit. It is my understanding that the gears interface on a 90 degree angle. I'm not sure of the size of the center hole so, attaching this to the differential carrier would be necessary if this option is chosen. 21/19 is a ratio of 1.105 (would it be possible to mount them in 19/21 so, a .904 gear ratio?
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Gearcases are highly loaded, and if the gears are not precisely aligned, will destroy itself quickly. They have to be shimmed and mesh precisely, taking them out of the case and installing in something else would be fraught, imo.
     
  12. Dieboat
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    Dieboat Junior Member

  13. Dieboat
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    Dieboat Junior Member

  14. Dieboat
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    Dieboat Junior Member

    Thank you Mr. Efficiency, your point regarding precision shimming is well taken. What do you mean by "highly loaded"
    Thanks again
     

  15. Dieboat
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    Dieboat Junior Member

    ?

    Is this different than an automobile differential?
     
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