1969 25HP Johnson high speed adjustment...

Discussion in 'Bubba's Outboards' started by dixiedrifter, Apr 23, 2006.

  1. dixiedrifter

    dixiedrifter New Member

    Messages:
    102
    State:
    Tennessee
    Need some advice on setting the high speed needle of my motor... I'm wanting to get it "perfect" as possible.

    When I rebuilt the carb, I gently seated the needle and backed it off 2 turns. Motor seems to be doing OK at this setting, but could probably be fine tuned a bit more.

    How many turns is the needle supposed to be set back when doing a readjustment and how do I know I got the correct fuel/air mix?

    Thanks.
     
  2. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    You've got 2 needle on that carb?
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That motor should have a fixed high speed jet if it has two then some one changed the carb out. any way this should help.


    This was written by a friend of mine and to me he is one of the best. I have learned a lot from this man.




    Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

    Setting the high and low needle valves properly:

    NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.


    (High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

    (Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

    When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

    --------------------
    Joe Reeves

    30+ Years With OMC
     
  4. dixiedrifter

    dixiedrifter New Member

    Messages:
    102
    State:
    Tennessee
    Your right!

    I didn't pay much attention to the parts list descriptions when looking at the diagrams.

    The upper needle valve is the low speed adjustment, not the high speed... that makes sense that the motor is running a bit rough at idle.

    And, there is indeed a fixed jet for the high speed running which explains why it runs so nicely when its WOT.