Dialing in an alignment on a v-drive

Discussion in 'Inboards' started by missinginaction, May 10, 2014.

  1. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    I'm ready to align my prop shaft and get the engine secured on the mounts.

    This is a run of the mill v-drive set up. The Walters drive unit is secured to a Velvet Drive that's bolted to a small block Ford V-8. Shaft is supported by a single strut, passes through the shaft log and bolts up to the drive via a split coupling. 1 1/4" shaft, 1 3/4 in shaft log. I'm replacing the original packing gland with a PSS because it's almost impossible to tighten a packing down by the shaft log since there is almost no space to work.

    I installed a new cutless bearing and have made up a simple wooden block that centers the shaft in the log. The shaft slides right in. Centered in the bearing and centered in the log. So far so good.

    I know what I need to do to get the engine aligned with the shaft. As with many v-drives it's very difficult to see what you're doing under there.

    I got to thinkin', "is there a better way?". I've decided to take a page out of the sterndrive guys playbook. When you align a Mercruiser you use an alignment tool and work by feel. When the alignment is right the tool easily slides through the gimbal bearing, into the coupler. I thought, "Why can't I use the same principle with my v-drive?"

    So I ordered a length of 1 1/4" OD steel tube. My plan is to slide the steel tube into position, mimicking the bronze shaft. Install the split coupling onto the v-drive, open it up a bit so the shaft will slide in and start sliding the engine around on the mounts. Shining a bright light onto the v-drive coupling will enable me to sight through the steel tube so that I can easily see which way the engine needs to go. The coupling is 3" deep. When it is lined up properly the shaft should slide in with no binding, just as is done with the sterndrives.

    I realize that a steel tube isn't a precision tool and I'll check it with a dial indicator. What I'm trying to do here is get into the ballpark and maybe into the infield with this alignment without killing myself. Then I can tweak it when the boat is launched.

    I'll let you know how it goes.

    MIA
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I don't think you will be able to sight .005", which is what you are aiming for.
     
  3. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    You're right, I can't sight 0.005". I'm wondering if I can feel it though. The idea is to get close using the steel pipe. Then I'll install the bronze shaft and finish the alignment in the usual way.
     
  4. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    For a rough estimate it makes sense. It should make the job faster.
     
  5. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    yes you will feel that shaft sliding in and out and you will feel it closer than 005.
    I have used that method before but used a solid couping to ensure the bore is parallel.
    If you can try it before you put the bearing in the skeg so you can also see how the shaft aligns with it and with the drag gone its much easier especially if it way out as when you move the engine you get to see exactly where the shaft is going in the skeg.
     

  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The human eye is capable of seeing a 003" variance, amazingly enough.
     
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