Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 97Get this manual
Carburetor Specifications SYNCHRONIZIN CARBURETORS
To Synchronizing carburetorsrefer to "TimingSynchronizingAdjusting" section
JET LOCATION FOR EACH CYLINDER
Carburetor jets and adjustment screw installed in the starboard side of the carburetor supply fuel to the port cylinder, jets and adjustment screw installed in the port side supply fuel to the starboard cylinderNOTE: The idle jet and back draft jet affect both cylinders
IDLE MIXTURE SCREW
For best running quality, the adjustable idle mixture screws
are set at the factory with the limit tabs pointing straight upIf adjustment is required, all idle mixture screws must be turned the same amount and the same directionTurning the idle mixture screws (recommended 18 turn at time)
RE-JETIING CARBURETORS FOR HIGH ALTITUDE OPERATION