Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 55Get this manual
Carburetor Adjustments Initial Starting Adjustment
If motor cannot be started, turn low speed mixture screw slowly inward (clockwise) until it seats lightly, then back out 1-114 turns(Turning mixture screw in tight will damage needle and seat This approximate setting will permit startingAs soon as motor starts, allow for warmup (run for several minutes)throttle engine back to idle for about one minute to allow RPM to stabilize, then make final adjustments
Carburetor Float Adjustment
FLOAT LEVER ADJUSTMENT
Invert float bowl coverSecondary lever (a) should belevelBend primary lever (b) if adjustment is necessaryFLOAT DROP ADJUSTMENT
Hold float bowl cover uprightDistance between levers should be 14 in (6.4mm) Bend tab (a) adjustment is necessaryFLOAT SPRING ADJUSTMENT
Low Speed Mixture Adjustment
1Start engine and allow to warm up (run for several minutes)Throttle engine back to idle for about one minute to allow RPM to stabilize2With motor running at idling speed while in forward gear, turn low speed mixture screw counterclockwise until motor starts to "load up" or fire unevenly from over-rich mixture3Slowly turn low speed mixture screw clockwise until cylinders fire evenly and motor picks up speed4Continue turning mixture screw clockwise until too lean mixture is obtained and motor slows down and misfires5Set low speed mixture screw halfway between rich and lean6Do not adjust leaner than necessary to attain reasonably smooth idling When in doubt, set mixture slightly rich rather than too lean7Check for freedom from cycling between idle and 2000 RPM (in forward gear)