2006 SD Johnson 4 Stroke 9.9-15HP Outboards Service Manual, Page 150Get this manual
POWERHEAD CYLINDER HEAD ASSEMBLY
Valve Seat Servicing
If the contact between valve and seat is not uniform, the valve seat must be refacedBoth intake and exhaust valve seats must have two chamfer angles, 150 and 45 0
If width is to low (narrow), reface valve seat using the 45 cutter 45+ +
Too high (wide) Too low (narrow)
IMPORTANT: Grind seat areas minimally onlyDo not grind more than necessaryClean up any burrs using the 45 cutter very lightly
Use 45 cutter to reface valve seat
IMPORTANT: Turn counterclockwise