Split coupler?

Discussion in 'Inboards' started by Downeast450, Mar 14, 2012.

  1. Downeast450
    Joined: May 2010
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    Location: Seal Harbor, Maine

    Downeast450 Junior Member

    I am removing the coupler from my Atomic 4's 3/4" shaft. I am considering a split coupler to replace it. Don Moyer sells one for the A-4. Direct drive prop shaft coupling, with split hub (3/4 inch).

    Has anyone used a split coupler? This one? Any reason why I shouldn't? Does it require "fitting and facing"?

    Thanks,

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  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you mean the one that looks like a straight pipe with a cut in it, the main drawback is alignment. With regular couplers you can align an engine with a feeler gauge. To align two shafts with straightedges only is really hard. If you mean a standard coupler with the split collar, they are OK. However, what is wrong with the old coupler. If the shaft is worn the split collar will clamp tight but will probably not be straight.
     
  3. Downeast450
    Joined: May 2010
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    Downeast450 Junior Member

    This is Moyer's coupler.
    [​IMG]

    [​IMG]

    I asked him about facing and fitting but got no special warnings about alignment issues. Why would this flange pose a special alignment concern? The old flange may not be usable. Most advice is not to use it because the fit will be too loose.

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  4. gonzo
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    gonzo Senior Member

    If you are using it because the shaft is worn out, the coupler will not clamp square to the shaft. If the shaft is OK, it is not necessary.
     
  5. Downeast450
    Joined: May 2010
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    Downeast450 Junior Member

    Gonzo,

    How do you recommend forcing the new "regular" coupling onto the shaft? The shaft is ok.

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  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I see nothing wrong about the Moyer coupling. Although the drawing doesn't provide exact dimensions, I assume that the bore is only a few mils larger than 3/4", just enough to insert the shaft without the use of tools.

    In the drive train of my boat I have used split collars with Allan bolts compressing an alloy steel sleeve over a 1" prop shaft. It transmits the torque of an 80 hp diesel engine.
     
  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Couplings can usually be tapped in with a dead blow hammer. If the shaft is OK, either type works well.
     

  8. Downeast450
    Joined: May 2010
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    Location: Seal Harbor, Maine

    Downeast450 Junior Member

    CDK,

    Thanks for the input. It seems like it should be a much simpler solution that the hot / cold, up and down the ladder to tap the shaft solution. My knees don't need all the extra flexing of coming and going from the limited space I am working in. It will save hours of time for this install and if I decide to change to a dripless packing in a couple of years removal will be a snap.

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