1993 rebuilt 200 hp evinrude. each carb has a mixture screw, the clymer manual does not say how to adjust each carb. right now each is turned out 4.5 turns- is this too much? engine runs extremly rich, and at present am trying to trouble shoot oil use problem. Could this adjustment be part of the cause. or is it just adjusting air/gas as oppossed to oil/gas? 