Re: update on problem with 1995 9.9hp no full throttle
The mixture screw on your motor will only adjust your slow speed jet on your carb. The slow speed jet is basically used for idling and trolling speeds. Clockwise turning will reduce the gas to air ratio providing a leaner mixture and counter-clockwise will increase the gas to air ratio, providing a richer mixture to the cylinders. As you may know, there is an optimum balance of gas to air that creates the best combustion. When you are sure the motor is operating properly you can simply warm up the motor and bring it to a slow idle in neutral. Slowly turn in the mixture knob clockwise about 1/8th of a turn. Give the motor about 10 seconds to respond. If the idle RPMs increase, reduce the throttle back to a slow idle and turn the knob in another 1/8th of a turn. Keep doing this until the motor sneezes, coughs and wants to stall. At that point, turn the knob counter-clockwise 1/4 turn and leave it there for good. You can reset the knob so that it points 1/2 way between rich and lean. Your slow speed jet is now set.
In any event, if you are having problems at the top end it is unlikely that the carb's mixture knob will have any effect. It could be other things to do with the carb but personally I would do that easy test I suggested before I did the harder job of cleaning a carb, probably to find out later my carb was fine. If you have an external spark tester, it would be good to know if each cylinder's ignition can jump a minimum of a 3/8" gap. If you have a compression tester, knowing the cylinders compression would also be very valuable. If you don't have either, at least confirm if both cylinders are running.
It is rare that the reeds create problems but if they do you will most likely see it in the single cylinder test I suggested. If you are only running on one cylinder, don't waste your time cleaning the carb. The carb feeds both cylinders so either your motor will be working fine or both cylinders would be acting up or dead.
