2001 Mercury Mariner 50-60HP Factory Service Manual, Page 175Get this manual
CARBURETOR
Idle Mixture Screw Adjustment
NOTE: Access to idle mixture screws can only be made by removing the sealing plugDrilling small hole in the center of the plug and using an awl to pry out the plug must be done with extreme cautionThe sealing plug is very thin and the idle mixture screw is located directly behind the plugIt is recommended that additional idle mixture screws be ordered for stock should the original mixture screw be damaged during drilling or the removal processIdle mixture screw adjustment is strictly regulated by the Environmental Protection AgencyHowever, if the carburetor is overhauled, the EPA allows the adjustment of the mixture screwsEach idle mixture screw (1 per carburetor) is located behind sealing plugThe sealing plug can be removed by carefully drilling small hole in the center of the plug and prying the plug out with an awlAfter mixture screws have been adjusted, new sealing plug MUST BE installed over each mixture screw