Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 195Get this manual
CYLINDER HEAD
3Perform the following adjustment steps: aTurn the driven gear and align the "1 111" mark on the driven gear with the "6," mark on the cylinder blockbAdjust the intake and exhaust valve clearance for cylinder #1cTurn the driven gear 1200 clockwise and align the "6," mark on the driven gear with the "6," on the cylinder blockdAdjust the intake and exhaust valve clearance for cylinder #2 eTurn the driven gear 1200 clockwise and align the "11" mark on the driven gear with the "11" on the cylinder blockf