Mercury 40 Service Manual page 230

CYLINDER HEAD
Valve Refacing Steps
Condition: The valve seat is centered on valve face but it is too wide.
Use
Lightly Li htl
Condition: The valve seat is in the middle of the valve face but it is too narrow.
Use
Condition: Valve seat is too narrow and it is near valve margin.
Use
Page 4A-34
Valve Seat Cutter Set
15 Cutter
60 Cutter
Valve Seat Cutter Set
45 Cutter
Valve Seat Cutter Set
15 Cutter, First
45 Cutter
55799
Desired Results
To reduce valve seat width
55800
Desired Results
To achieve a uniform valve
seat width t idth
55801
Desired Results
To center the seat and to
achieve its width hi it idth
90-828631R3 MARCH 1999