alpha one outdrive - hit log

Discussion in 'Sterndrives' started by rollyh, Sep 6, 2010.

  1. rollyh
    Joined: Sep 2010
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    rollyh newbe to site

    I have a question I have a 92 chaparral with mercruser alpha one out drive. Yesterday I hit a log ,tip of prop shows ding but it wont go when I put in gear. I pulled the boat out I put shifter in gear and I can turn prop by hand both ways maybe a little drag in the direction I have in gear not much tho. My question is there a shear pin on the prop or did it strip a gear ? I am a good mechanic so I would like to do my self if I can any help would be appreciated
     
  2. baeckmo
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    baeckmo Hydrodynamics

    First check if reverse is functioning; if yes, the outer shell of the lower shift cable may be broken. Its steel wires corrode close to the drive. Since it (mostly) is "push-for-forward", the shell moves away from the drive and no action is achieved.
     
  3. J3
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    J3 Junior Member

    For completeness, no there is no shear pin on the prop. The mercruiser alpha props had a rubber hub. A "spun hub" usually allows idle speed but the more power you apply the more it slips.
     
  4. CDK
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    CDK retired engineer

    If Baeckmo is right you are one lucky *******.
    You may be even luckier if the shift cable is OK but the shift finger is not in the fork under it but jumped out.

    Less lucky people have the lower housing cracked after a log hit. And I know one case where even the gimbal housing was wrecked, but that was a submerged rock, not a log.
     
  5. rollyh
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    rollyh newbe to site

    I could not find any outside damage to the unit. When it was in the water and I would put it in gear it would do nothing forward or reverse but I would not also here it grind when I put in gear also. I took out of water if I put in gear I can turn prop easy on way hear slight clicking little drag the other way . Did I strip a gear in lower end . is it something I can do my self Iam mechanically inclined .
     
  6. CDK
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    CDK retired engineer

    With the boat on dry and the drive fully tilted and turned to one side, you can see the simple gear switch mechanism. Push it with your thumb and rotate the prop: it will lock in one direction, turn free in the other.

    To repair any damage except a bent fork (you can bend it back up after aligning the finger) the drive must be removed.
     
  7. gonzo
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    gonzo Senior Member

    Most likely the dog clutch and gears are stripped. The other possiblility is a sheared vertical shaft. You need to split the unit to first check which part has the damage.
     
  8. rollyh
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    rollyh newbe to site

    Well I tried to turn it I think were you mean is the shift mechanism I could not turn it even with pliers so i put it in gear with shifter fwrd . I could turn prop counterclockwise and I could hear a suction from lower unit I think maybe like a water pump .and I would turn it clock wise and turned free but clicking sound. I would put shifter in revers and would do the same thing but in opposite direction. am I still a lucky ******* or unlucky one .
     
  9. gonzo
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    gonzo Senior Member

    Sounds like a broken clutch. Usually the gears get damaged too.
     
  10. rollyh
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    rollyh newbe to site

    rollyh

    Does that mean I have to I guess take apart the lower end . do I need special tools for this or can i change it will i just use all the same shimms
     
  11. CDK
    Joined: Aug 2007
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    CDK retired engineer

    No, if you hear the suction sound from the pump when turning the prop, your luck ran out.
    The vertical drive shaft through the pump can only be rotated by the engine. If you can do that by turning the prop, the shaft has snapped into two pieces, or....(less likely but possible) the engine coupler is gone.

    For the shaft you need to remove the lower part of the drive. You can do that with the upper part installed in just a few minutes. One bolt (Allen head) is hidden under the trim tab, which has to be removed first, the others you can clearly see.

    Be prepared for the oil dripping out!
     
  12. rollyh
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    rollyh newbe to site

    thanks guys i think i'm gonna start working on a saturday can i have to pull the whole world drive off anywaysto change the bellows one is bad I will take your advise thanks for the help
     
  13. rollyh
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    rollyh newbe to site

    Update -- I took it apart the main shaft I think they call it the drive shaft that goes in the gear case is broke. It broke off in the top were it goes in the top end.Question can I replace that with out having to set up the gears if I just replace the drive shaft. Or does the gears have to be reshimmed . Also from the prices I have talked to people about repairing it whats everybody's impression on using after market gear case I have seen them on the net for 800 bucks.
    Thanks for all your help.
     
  14. powerabout
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    powerabout Senior Member

    is that $800 new? if so get one.
    If you hit something, even thought the drive shaft broke at its weak point the gears in both the top box and lower unit could still be damaged.
     

  15. CDK
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    CDK retired engineer

    The shaft has a favorite place to break: where the O-ring of the upper gear case has worn its surface. It is the weakest point in the chain.

    You need to replace just the shaft and the seal.
    This may also be a good time to replace the impeller and the bellows of course.
     
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