125 mercury

Discussion in 'Bubba's Outboards' started by gasman711, Jul 17, 2007.

  1. gasman711

    gasman711 New Member

    Messages:
    3
    State:
    Illinois
    I have a 125 mercury #3115197 I don't have the year. I can not get it to run out at 5500 rpm it will only go up to 4000. carb is open all the way. had carb rebiuld, new flywheel put on. Can you help. Thank you .
     
  2. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Check the pitch,dia and hub of your prop.If you have the wrong prop nothing you will do will matter.Also do you know if it is firing on all cylinders?
     

  3. Mr.T

    Mr.T New Member

    Messages:
    2,553
    State:
    MO
    Also make sure your tachometer is set up properly for your engine. Most modern ones have an adjustment on the back to accommodate the timing characteristics of various engines. You'll probably need the help of a repair shop to verify the setting.

    If the motor has been used with that same tach for a long time, this probably isn't your issue. But if it's been recently installed on the boat, it could be.
     
  4. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill


    Does this engine have 4 cylinders or 6. They made several of those 125 and does the serial number have a letter in front of it or is it as you wrote here.

    The first thing is to get a Manuel to trouble shoot this engine as it has several components that depend on each other that can cause this type of problem Some you can test but others you can't without proper equipment and that is by ruling out what is good and what is left is the bad.

    First things first. Is this a new problem or is it and old problem and is this motor a new to you motor?
    Do a compression check and spark test without this its just a guessing game.
    If you don't know how to do these tests then get a Manuel or go to the local library to borrow one. It is most important to do this to properly diagnose your problem or you will be throwing parts at that beast and that can get expensive.
    Get back to me with the readings on the compression and spark. You have to have a spark tester because grounding the plugs against the block just doesn't do it.
     
  5. gasman711

    gasman711 New Member

    Messages:
    3
    State:
    Illinois
    It is a inline 6 compression is 135 to140 ,spark is good on all 6. Motor was in shop to have work done .has never run good only had it on water 4or5 times.
    No letter on ser # it is 3115197. prop is 19 pitch thanks Dave
     
  6. gasman711

    gasman711 New Member

    Messages:
    3
    State:
    Illinois
    CAN SOME ONE TELL ME THE YEAR OF MOTOR?
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Is there any way you can post a picture of the front of the motor The cowling I need to see what color the bands are around it. Does it have a distributor and a model that says 1250
    The only thing I can come up with on that serial number is an old tower of power inline six 1250 1969 model. If this is true then you are at your working rpm's at 5500