Lower Unit Leak?

Discussion in 'Bubba's Outboards' started by miichael, Jul 27, 2006.

  1. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    I just purchased a 1976 Mercury 20HP and the motor seems to run great. Both cylinders have around 90psi compression (on pull start) and runs good. However the lower unit has a leak. I took out the drag plug and air screw and nothing came out. I put lube in it and it leaks out around the prop. I pumped lower unit with air and i can hear the air leaking from behind the prop.

    What seals are back there?
    Do I have to drop the whole lower unit?
    Do I need any special tools for the job?

    Any info on this would be great!

    It is a 1976 Merc Model 200 20hp.
    I ordered a repair manual today should be here next week.
     
  2. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    You can pull the prop and see the seal. It ain't that big of a job to change it out. Go order the seal and you will see how it sets in it.


    I'll up load you a diag of that lower unit tomorrow.
     

  3. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    If thats what it is i want to go ahead and order it now that way when my manual gets here i can change it out. The nut behind the prop i think takes a special tool it has 4 cut out notches in it like a spindle nut on a car.

    Do i have to drop the lower unit? If not im not going to change the water pump just yet going to try the boat out before i change it.
     
  4. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
  5. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Yes, that's more than likely what's leaking.

    You might find when you get your manual that there's two seals in that area that are installed back to back. It might also recommend getting a new o-ring for the bearing carrier that you have to remove to replace those seals.
     
  6. Mr.T

    Mr.T New Member

    Messages:
    2,553
    State:
    MO
    If you're working on the motor anyway and especially if you don't know when the water pump was changed last, go ahead and get the new parts and replace it now. It'll be a lot cheaper than buying new pistons later when the pump gives out.
     
  7. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    I would be somewhat concerned that "Nothing" came out.:angry: No telling how long it was operated like that.T is giving you good advice also to just do a waterpump rebuild kit at the same time.Get rid of whatever fuel was in it or came with it.Get fresh fuel and add stabilizer and a can of Ring Free or other approved carbon remover.Might as well start out right if you want the engine to last.New plugs wouldn't hurt either.:smile2:
     
  8. Hootowlc3

    Hootowlc3 New Member

    Messages:
    409
    State:
    Florida
    What is ring free????
     
  9. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Ring Free is YAMAHAS de carbonizer I believe.Virtually all Out board companies make a fuel additive that removes carbon> This prevents ring sticking,coking and other bad things from happening to your cylinders.PRI-G fuel additive has a carbon remover built in.In any case it is a very good Idea given todays dirty gasolines to use a can once or twice a year.:smile2:
     
  10. miichael

    miichael New Member

    Messages:
    380
    State:
    North Carolina
    I cant get that nut off behind the prop? it has 4 notches for a special tool like a spindle nut on a car but i cant get the nut to budge. I have a tool that fits it but cant get it off. Is it righty tighty lefty loosy? or it it backwards? any info?
     
  11. savage308

    savage308 New Member

    Messages:
    399
    State:
    Victoria, Texas
    Miiachel
    Put a small table or brick just under the prop before you take it off. Put something stable on the table or brick just under the prop so it almost touches. Then spin the prop slowly and see if all the blades are the same distance from the item you put under it. This tells you if you have a bent shaft or prop. Changing the waterpump is a great idea and highly recommended as you don't know how good of shape it is in. Hope this helps.