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Lower unit knocks

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  • Lower unit knocks

    Hello, I'm new here and am glad to be a part of this wonderful forum. Now my issue. I have a 2013 90hp 4 stroke mercury. I replaced the waterpimp impeller. On reassembly when fighting things up I heard a snap. When I restarted it, it ran and pumped fine, but when it put it in gear it made a knocking noise. It goes in and out of gear ok, but seems to jamb slightly while engauging. It has a knock when in gear, forward and reverse(not as bad reverse). When the engine is in neutral the prop turns freely, with no grind or any resistance. Any thoughts would be appreciated. Thanks

  • #2
    You pulled it together with the bolts ?----Did you turn flywheel to engage driveshaft splines before tightening the bolts ?

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    • #3
      I thought so. The housing was about 1/4 out when I tightened the bolts. Was that too far out??

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      • #4
        If something was out of alignment, where would the likely damage be?

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        • #5
          Originally posted by Fladgelator@hotmail.com View Post
          I thought so. The housing was about 1/4 out when I tightened the bolts. Was that too far out??
          As Raceone asked; Did you turn the flywheel while bolting it up? how much pressure did it take to bolt it up? how loud was the "snap"?
          I would drop the LU and check the shift-shaft & bench test it's mechanism
          "Success is walking from failure to failure with no loss of enthusiasm." - Winston Churchill

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          • #6
            The snap sounded like breaking a pencil. I was thinking about the reassably and forgot a detail. I had the control in drive when takin apart. During the impeller install, the lower moved into neutral. I didnt put the controller back into neutral when I bolted up. So I'm thinking when I failed to do that the shift shaft snapped something in the lower unit. Thoughts?

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            • #7
              Regardless (I think) you'll have to drop the the LU & sync. the set up. (I'm not familiar with your motor, but only with the older Mercs.)

              But the important thing is not to have too much tension on the bolts when bolting up & turn the fly-wheel when it's close to "on" this way the Drive-shaft slips into place.

              If everything is lined-up properly it should/ could slide on all the way till the LU meets the mid-section, yes gravity works against us that why we use the bolts to do the last inch or two.
              "Success is walking from failure to failure with no loss of enthusiasm." - Winston Churchill

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              • #8
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                Yup, I'm going to drop the unit again. Thanks for the help! I'll follow up after I see what happened, so others hopefully wont do the same thing!

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