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  1. #1

    Default Lower unit will not come off

    I have a 1978 mercury 200 20hp. I have removed all the nuts to get lower unit to drop but it seems stuck on forward end. I want to replace water pump but dont want to break anything getting to it. Any suggestions.

  2. #2
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    17,063

    Default Re: Lower unit will not come off

    There's another nut hiding above the trim tab.

    Jeff

  3. #3
    Join Date
    May 2013
    Location
    TX.
    Posts
    556

    Default Re: Lower unit will not come off

    As I recall, a hex socket screw is accessible from the top side, under a little cosmetic clip about the size of a dime. Remove that hex bolt and drop the trim tab. Then look from underneath the AV plate up in the hole and you will see another bolt. That's your smoking gun.

    If you have that bolt off, and it won't drop, your drive shaft is probably stuck in the bottom of the crankshaft. Numerous tricks on the www boating forums as to how to dislodge that.

    One other thing is your shift shaft up at the front of the LU. Ensure that you watch that joint as you separate and ensure that the mid section shift rod spline comes out of the coupling...squirting with PB Blaster or other quality penetrating oil is a great idea. If you see the coupling, seals and all coming up out of the LU, stop and resolve that problem because if you pull the shift shaft stub up out of the LU, it separates from the "Cam Follower", pushed out of place by the spring behind the clutch dog spring and you usually have to open the gear box to get it back in position to restab the shaft splined stub.
    Last edited by Texasmark; 03-04-2021 at 07:37 AM.

  4. #4
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    4,237

    Default Re: Lower unit will not come off

    How far will it drop before it hangs up? Saltwater motor?

  5. #5

    Default Re: Lower unit will not come off

    It doesnt drop at all. There is free movement under trim tab and if prying top forward stud a little there too. Seems stuck in the middle

  6. #6
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    4,237

    Default Re: Lower unit will not come off

    Gotta be rusted driveshaft into the crankshaft. Try mixing 50/50 acetone and auto trany fluid. Shake it up and use right away. Set it upside down on the floor, put some wedges into the opening and squirt the mixture in so it runs down driveshaft to the splines at crankshaft. Leave overnight, then give your wedges a few light taps....see what happens.

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