How do I adjust the Idle mix screw on a 2004 Mercury 15hp bigfoot

How do I adjust the idle mix screw on a 2004 mercury bigfoot 15hp?

I have drilled out and removed the factory brass plug and exposed the screw. It was set at 6 and 1/4 turns open from fully closed.

The symptoms I am trying to address are:
Some difficulty starting warm and cold. Usually have to use throttle advance to allow extra air.
Flat spot and stumble between idle and part throttle.
It is very difficult to obtain a good trolling speed. It either wants to idle or race.
It has been making oil for some time and this oil change smelled of gas.

This is a kicker motor and runs for days just above idle. It has about 14 days of run time since this springs oil change and is now about a 1/4 liter over full of oil.

I set the screw at 1.25 turns open and the idle got smooth and the flat spot dis-appeared but I would really like to use the proper procedure. I am working on muffs in my driveway and would like to have it running good before I go to the lake.

By the way my electronic service manual is silent on the matter and does not even show the adjustment screw or plug in the exploded parts diagram.

Thank You!

Thanks.

I appreciate the advice. Based on the way this motor has runs I suspect maybe the carb is over fueling and unburned fuel is washing down into the crankcase. I try to troll right in the middle of the "stumble" so I suspect unburned fuel is accumulating I would like to set the carb correctly and run it to check. I would rather deal with the fuel pump (if required after the carb) in the winter when my family is not waiting to use our boat. I realize the fuel pump is minor but down time waiting on parts can be an issue and we really only use this boat a few months a year (August is prime time).

I changed the kicker oil to get through to the fall.

Can anybody tell me how to set the ide mix screw?

Thank You Everybody!

I doubt very much that over-fueling is adding 1/4 of a litre of fuel to your crankcase. This is a 4 stroke, and any un-burnt fuel will be expelled from the combustion chamber during the exhaust stroke. Did you check the spark plug condition? (wet plugs would indicate over-fueling). You don't need any parts to inspect the fuel pump, and an outboard that has gasoline in the crankcase is just plain dangerous.

Thanks

Yes understood. That makes good sense. I will deal with the diaphragm issue but I will still need proper carb tuning instructions please.
Unfortunately my trucks electric shift transfer case just became a higher priority.

Jeff

Update. This engine is running smooth and strong. The issue was with the fuel mixture screw which was sealed under plastic to prevent adjustment. I removed the tamper resistant material and adjusted it. It runs like a champ now and does not "make" oil anymore.
I am sorry that I do not recall the adjustment anymore but it was worth making the change. Easy start warm and cold. No Flat spot. No stumble. No fouled plugs. Just good running smooth clean efficient engine.