1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 159Get this manual
CYLINDER HEAD
Adjustments
Valve Clearance
IMPORTANT: The timing belt must be installed and gears in the correct position or valve damage may occur1Remove components: Flywheel covermanual starter depending on electricmanual start versionDriven gear coverDisconnect inlet and outlet fuel pump hosesCylinder head cover