Idle adjustment on 03 merc. 75 hp

Discussion in 'Bubba's Outboards' started by ohiorivercat, Jul 24, 2007.

  1. ohiorivercat

    ohiorivercat New Member

    Messages:
    26
    State:
    kentucky
    ive got a 2003 mercury oil injected 75hp on my boat ...i had the carbs rebuilt right after i purchased it this year it had been sitting a good while ...it runs good starts good other than being a little cold natured..my problem is it seems to be running to rich at idle (running rough and a little more smoke than normal) and sometimes (not always)if you pull the throttle back to idle it will die but it starts right back up with no problem...is there a standard adjustment on the mixture screws????
     
  2. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    chad I am taking a wild stab at this because I haven't been in contact with an 03 merc yet but I would guess that both those jets are fixed low and high speed. You might have a plug failing intermittently at low idle or it could have a fuel line sucking air at low idle.
    When it does idle what are the rpm's at idle in the water?
     

  3. ohiorivercat

    ohiorivercat New Member

    Messages:
    26
    State:
    kentucky
    FROM WHAT THE TACH READS 600-700 RPMS WHEN AT IDLE WITH ENGINE WARM
     
  4. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That tach reading is about right when in the water and in gear if not in gear then it needs to be idled up a tad. Does that carb on it have any adjustment screws on it. It sounds like it may be running a little lean at low idle or you have some trash inside one of them that is stopping the low idle cirturty up when at idle. Check all your fuel lines and bulb and make sure its not sucking air some where. Make sure the carbs are tight on the motor.
     
  5. ohiorivercat

    ohiorivercat New Member

    Messages:
    26
    State:
    kentucky
    all three carbs have a adjustment screw.....there tight and just had a fresh cleaning/rebuild by dealer i called them to see what they said and they wanted to have me bring it back but i would rather try and straighten it out my self instead of it sitting at dealer for 2 weeks......the screw i see on the carbs is a mixture screw im sure i guess it idle it up has to be done in the linkage itself....i just wandered if there was a basic setting to go by on the mixture screws
     
  6. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Those carbs need to be adjusted while under a load. You run the screws in until they are gently seated , not hard now because it will damage the ends of the needle. Turn them out about 1 1/2 turn will be a starting place.

    Turn each screw 1/8 th turn increments. counter clockwise You have to do each carb individually and allow about 10 seconds between adjustments to let the motor to adjust itself to the carb setting. You back the needle out until you hear the miss in it. Then you turn it back clockwise until it starts to stall and then turn counterclockwise 1/2 turn and that should have it set.

    When you accelerate if it stalls you need to turn the needles counter clock wise until the stall comes out. Remember do this 1/8 turns at a time and under a load.