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Finding rough engine alignment. Mercruiser-gctid469908

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    Finding rough engine alignment. Mercruiser-gctid469908

    A 96 Mercruiser 5.7. The engine had been out by the PO. I put in a new gimble bearing. When I check the alignment, the tool gets stuck long before it bottoms out.. It's very hard to remove. So, I'm assuming that the engine is far out of alignment.

    *** How do you get the engine close to aligned, after an engine has been out? ***

    I've just looked down past the gimble bearing and it's pretty hard to determine whether the engine should go up or down. I tried laying a tape measure in the hole and it's still pretty hard to determine.

    While I'm asking questions, what size bolts are on the typical Mercruiser engine mounts. I know they're bigger than 7/8s.

    Thanks in advance.

    #2
    Craig.... see attached image below. It demonstates what the alignment procedure is trying to achieve.

    NOTE: the Gimbal Bearing articulates within it's hemisperical support housing. This means that even if the drive coupler was perfectly aligned, if the bearing itself is not centered with the coupler center line, you may feel this in the form of resistance.

    Insert the alignment tool just enough to move the center section of the bearing..... and then try going into the coupler again.



    Attached files [img]/media/kunena/attachments/vb/774419=36927-Drive Coupler alignment explained 4.jpg[/img]
    Rick E. Gresham, Oregon
    2850 Bounty Sedan Flybridge model
    Twin 280 HP 5.7's w/ Closed Cooling
    Volvo Penta DuoProp Drives
    Kohler 4 CZ Gen Set

    Comment


      #3
      Thanks Rick. Your post and this one answered the question. Everything lined up perfect. http://forums.iboats.com/mercruiser-...os-443992.html

      Comment


        #4
        Monterey10 wrote:
        • 1 wrote:
        • So, your saying that the alignment is as much straightening the bearing as it is adjusting the engine.
        • I would imagine that straightening the bearing would be the first priority...



        • 1 wrote:
        • Not actually.

          I'm suggesting that you may need to align the bearing so that when the tool is approaching the coupler splines, it is not obstruted by the bearing being off kilter.
        • Correct!



        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment


          #5
          The absolute best and only way IMO to get alignment "in the ballpark" is so simple. Get yourself a piece of 1 inch round stock, perfectly straight.This goes into the splines easily(a bit too easily a few thou thicker would be nice but the 1 inch works fine.)Get a flashlight and see how it appears to centre in the gimbal bearing. Should be equal all around.Remember I said its a bit too small?Sort of stir it around to get the feel of how much play is there and then holds it in the middle or average position.See how it centres on the gimbal brg. You should now rotate your engine in 90 degree increments and repeat,since gimbal bearings are famous for not being 100 percent true.If after all this(takes about 2 minutes if youve got an assistant to crank engine)you see that its always low or always high, you know which wauy to adjust alignment.Adjust alignment a bit and repeat above prcdre.If you do this procedure with reasonable care, your alignment bar will go in"2 fingers" when youre done.Some would say sell the alignment bar its redundant.

          Comment


            #6
            Even a broomstick would be helpful to get you into the ballpark.
            2007 Discovery 246
            300mpi BIII
            Welcome island Lake Superior

            Comment


              #7
              It would be nice if it was that simple.

              Look at the geometry between the gimbal bearing vertical axis, and the rear engine support vertical axis.

              Now look at the horizonal geometry and location of the coupler..... compared to these two axis.

              This geometry is such that the center-line of the coupler must align with the propeller shaft (aka front drive shaft) center-line.

              If the two shared an axis, alignment would be much easier.

              But as it is........ if the alignment is off, the shaft spline contact against the females coupler splines, will be continuously changing pattern.

              Changing wear pattern is what wears these splines out.



              Here is the tool dimension. The foward tip is where the grease pattern reading it taken from.



              Like said.... if both shared the same axis, the coupler alignment may not be as critical. The universal joint assembly will take care of some alignment issues AFT of the Gimbal Bearing and FWD of the upper drive unit.

              That's it's job anyway ...... or we would not be able to turn Port/Stbd, or trim the drive up.

              Ultimately the goal is to achieve a nice, even, radial contact between the male shaft splines the female coupler splines.

              IOW, even while both the shaft and coupler are rotating 1:1 with each other, we do not want the splines to be continuously changing major contact at either the 12:00 O'clock position, or the 6:00 O'clock position..... (depending on whether the engine is too high or too low).

              The Port to Stbd engine location geometry is fixed.... so there's no concern with the 9:00 O'clock or 3:00 O'clock positions with this.

              Attached files [img]/media/kunena/attachments/vb/774504=36933-Drive Coupler alignment explained 3.jpg[/img]
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment

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