Oil leak on lower unit

Discussion in 'Bubba's Outboards' started by shortbus, Oct 27, 2006.

  1. shortbus

    shortbus New Member

    Messages:
    459
    State:
    indiana
    I have a bad oil leak on my 87??? 25hp Mariner. The oil is coming from where the lower unit bolts to the upper part. Coming right out of the little crack. The oil doesn't apear to be LU oil but more exhaust type oil. There are several small holes in the casting around the water intake and the oil seeps out of these also. I do alot of idiling with this motor and was wondering if this is making the motor load up by not cleaning it out. Any clues to why the oil would be coming from the mating surface of the LU??? I will try and get a pic of where the oil is coming from and post it up.
     
  2. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That sounds to me like unburned fue put some sea foam treatment in it and try to clean the fuel system out. If that doesn't help much then I would tear the carb down and rebuild it. You are putting more fuen in then it is burning and it is escaping thru the exhaust.

    Another thing that will put it where it is , is a lower power unit seal shot but that will make the motor run rough most of the time. Pull the plug on the lower unit and make sure there is no water intrusion before you start on the other stuff and that will let you know if its rising up thru the seal below the water pump.
    I'll check and see what plug is recommended for that motor.
     

  3. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    You doing alot of idling with an older engine has surely loaded it up with carbon.

    Bubba, point him in the right direction for a decarboning of that engine, please.
     
  4. shortbus

    shortbus New Member

    Messages:
    459
    State:
    indiana
    Thats what I was thinking, sometimes I have to rev the motor a bit because it starts to idle rough. when I put the lower unit back on from the rebuild i noticed a small metal tube that slid over the input shaft. The tube had two o-rings on the outside of it. Could these o-rings be bad or not seated right? I was thinking they might seal off exhaust? If so are these just regular o-rings or do they need to come from a merc dealer?
     
  5. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    This engine has recently been rebuilt? Was the carb done also?

    Start from square one, and do an ignition check.

    Because of all the changes made and variences between engine's and hp, it requires Bubba and I to look into service manuals. Do you have the book on that engine?
     
  6. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Do a decarb first. Get you a bottle of sea foam or engine tuner. Sea foam is my choice. Put you a gal of fuel mix in a portable tank and mix about 3 or 4 oz of sea foam in it. Put the muffs on in the yard and run about 1/3 or 1/2 of mixture at idle and then remove plugs and squirt some inside plug holes while engine is warm and let it set foe an hour. Take it to the water and run it at wot for a few min and then let it cool for about fifteen min then put some more in the plug holes and run it for about 15 min at WOT.

    Then go back to your regular mix and add about 2 oz of sea foam to the mix and run like you normally do. This should clean all the carbon out. After doing all this then change plugs. I would add 2 oz of sea foam every time I filled up the fuel. this is a good stabilizer and cleaner to.
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill



    Bob is spot on with this suggestion her with the ing check. Every thing needs to be fireing right for it to work properly. I will see if I can find anything on the o rings.
     
  8. shortbus

    shortbus New Member

    Messages:
    459
    State:
    indiana
    Sorry for not explaining the rebuild. Just the lower unit was rebuilt,not the top end. I had the merc dealer rebuild the LU and I installed it back on. I do not have a book on it. I will decarb the engine with the sea-foam like you said.