Prop Shaft Nut 1976 20hp mercury

Discussion in 'Bubba's Outboards' started by miichael, Jul 31, 2006.

  1. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    I cant get the prop shaft nut off my 76 20hp mercury. I took the prop off and there's a nut that has 4 notches and i have a tool that fits it but i cant get it to budge. Is it standard rotation or is it threaded backwards? Trying to get the nut off so i can replace the prop shaft seals.
     
  2. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    I've got a 20 at the shop, I'll look tomorrow, but I don't remember a nut being on there after you take the prop off. Should be a thrust washer. Don't hurt anything till I get back with you.
     

  3. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    Thanks alot. I wont tear nothing up untill i hear back from you. I tried and tried to get the nut off no luck. let me know how to get it apart.
     
  4. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    First of all, what confused me, and that's easy to do, was you calling this SPANNER nut, a prop shaft nut.

    After you take off a prop, there's nothing on the prop shaft but a thrust washer that slides off.

    The nut your referring to is screwed into the lower unit housing. not on the prop shaft. It holds the "BEARING CARRIER" in place

    Terminology is a good part of communication, so try not to confuse me again. I'm old and cranky:crazy:

    Now back to this big round nut that's not screwed onto the prop shaft.:confused2:

    I've had to use acetyline heat around the outside area of the lower unit to break these nuts free. You can try map gas if you don't have acetyline. Be careful of acetyline, it'll make aluminum disapear. Always keep your torch moving. You want to heat not evaporate the metal.

    Some have saltwater corroded so bad that I had to drill and bust the nut.

    It unscrews counter clockwise, like most everything you've ever unscrewed.

    Upon reinstalling the bearing carrier, use a gasket sealer around the big o-ring you'll find around the carrier. Don't forget to drain the lower unit oil before starting this...
     
  5. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    So i have to take that spanner nut off to replace the inner and outer prop shaft seal?
     
  6. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Yeah Mike, you have to take it off, then slide out the bearing carrier. It comes out with a bit of resistance due to an o-ring seal. Just pull on the prop shaft and it'll all come out together.

    Once that's done, slide the bearing carrier off the prop shaft and take out the seals in the bearing carrier. Replace with new ones and put things back together in reverse order.

    Use a gasket sealer on the big o-ring as a lubricant when you reinstall the bearing carrier and prop shaft assembly.

    Don't forget to clean the threads of the lower unit and the spanner nut before you put it all back together.
     
  7. Mr.T

    Mr.T Active Member

    Messages:
    2,554
    State:
    MO
    I think you're asking for trouble if you're trying to do this work without the benefit of a service manual (Clymer or whatever).

    Bob certainly knows his stuff and can talk you through it, but having a book with pictures and step-by-step instructions trumps advice on a web bulletin board! Plus you won't have to wait hours for the "next step" if you get in the middle of the work and find yourself stumped by something unexpected.

    Get the service manual and this whole process will become a lot easier. It's a good investment of $25 if you're going to have the motor around for a while. Any local marine shop should have the manual, and they're available at numerous online sources.
     
  8. Bobpaul

    Bobpaul New Member

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    3,039
    State:
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    Why do I always forget to add the important stuff.

    I've got many manuals and use them frequenlty
     
  9. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    My manual should be here tomorrow. I just got the boat and ordered the manual the same day :big_smile:
     
  10. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    I also return to the manuels on a regular basis. I have some orignal manuels that was produced back in the 50's They are priceless when working on something and your old mine draws a blank. Another good tool is when you are tearing that unit down take a photo step by step and you can reverse it when going back together. That also is priceless.