Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 115Get this manual

CYLINDER HEAD
NOTE: If res urfacing the valve seats is required, resurface the valve seats to the specified angle shown in chartb

Valve Seat Angle Specifications

15 45 60 0
CORRECT VALVE SEAT POSITION

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives