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  1. #1
    Cadet
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    Default Belt Change Merc 120

    I have to change the alternator belt on a 1983 Merc 120 Serial#6273129. A hunk of the front motor mount needs to come out to release the belt.Do I need to support the engine while it is out and/or realign the engine after the change? I have the Merc manual #3. It shows the mount but doesn't say anything about it. Thanks

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Belt Change Merc 120

    If you happen to have power steering, remove the PS belt (A)Then remove the 2 bolts (B) holding the port side of the motor mount. Pry the spacer (C) out, replace the belt. Put the spacer and bolts back in, tighten belt, install PS belt if applicable, and go boating.
    Don S.


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  3. #3
    Senior Chief Petty Officer
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    Default Re: Belt Change Merc 120

    Put a block of wood undr the oil pan to support the engine and pull the motor mount. you won't need ti realign it as long as you do not move the lower nut on the motor mount ajustment screw.

  4. #4
    Cadet
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    Default Re: Belt Change Merc 120

    Great! Thanks for the help. This little 4 banger doesn't have power steering. I was just concerned that she'd sag with those bolts out.

  5. #5
    Seaman Apprentice beauff's Avatar
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    Default Re: Belt Change Merc 120

    I was wondering this myself. It worked great.

  6. #6
    Petty Officer 1st Class
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    Default Re: Belt Change Merc 120

    I have an OMC version of that motor. Buy 2 belts and snap tie the second one in, but out of the running belts path. Then when your on the water with only your "in the water" tool box, if you blow the belt you can change it in a matter of minutes, vs tow, ramp, trailer, home, blah blah blah. Enjoy!

  7. #7
    Seaman Apprentice
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    Jun 2006
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    Default Re: Belt Change Merc 120

    This old post hope someone is still watching.. I have a mercruiser 165 inline 6.. I tried removing the bolts that Don S described, but the lower bolt hits the engine compartment when you back it out and I can't get it out of block "C". Is there a workaround for this or a different trick for my engine?

  8. #8
    Fleet Admiral
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    Default Re: Belt Change Merc 120

    Same for the inline 6, you need to modify the engine compartment. sounds like you originally had a 4 in there not a 6
    NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

  9. #9
    Seaman Apprentice
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    Default Re: Belt Change Merc 120

    Somthing still doesn't seem right.. I drilled out my engine compartment so that could back the bolt out and eventually got the spacer out... but then as I started looking closer at the drive pulleys I noticed there was minimal gap between them and the motor mount.. there's still no way to squeeze a belt through with this procedure.. do I just have an oddball or has anybody else had this problem.as for the motor being non-stock.. it's possible, but not likely.. the boat's a 78 and my father-in law had it since 84.. unless the first owner swapped out the engine in the first few years it must be stock..

  10. #10
    Petty Officer 1st Class
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    LaGrange GA
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    Default Re: Belt Change Merc 120

    Did the motor drop a bit when you pulled the spacer,with rubber(isolater) motor mounts you may be able to pry a bit and get the space you need but be carfull where you apply the force to do this make sure its a solid point,like from the mount to the center of the crank pully.

  11. #11
    Petty Officer 2nd Class llerrad's Avatar
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    Ontario, Canada
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    Default Re: Belt Change Merc 120

    Don't forget to put on an extra belt and tie it out of the way for the next belt replacement. Save taking off the mount again.
    Cams and Carbs no Sails here

  12. #12
    Petty Officer 3rd Class
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    Default Re: Belt Change Merc 120

    tony dz, look again at the diagram. It might not route between the pulley and the mount. I believe the belt goes around that mount. That's a good idea about putting two on.
    1984 16.5 3.0 L OMC Stringer 400
    1983 17.5 3.0 L Mercruiser R

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