1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 166Get this manual
CYLINDER HEAD
7Remove keepers, upper seats, springs, seals, lower seats, and intakeexhaust valves
NOTE: Seals are not reusable
a-Keepers (8) b-Valve Spring Seats-Upper (4) c-Valve Springs (4) d-Valves-Intake (2) e-Valves-Exhaust (2) f-Valve Spring Seats-Lower (4) g-Valve Seals (4) (Discard)