Mercury FourStroke 2.5 Service Manual page 114

7. Start with the 45° cutting tool to clean up any pitting or rough surface of the valve seat.
45°
8. Use the 30° cutting tool to adjust the contact width of the top edge of the valve seat.
a
9. Use the 60° cutting tool to adjust the contact width of the bottom edge of the valve seat.
a
10. If the valve seat contact area is too wide and situated in the center of the valve face, use the 30° cutting tool to cut the top
edge of the valve seat and the 60° cutting tool to cut the bottom edge of the valve seat, to adjust its contact width.
o
30
a
11. If the valve seat contact area is too narrow and situated near the top of the valve face, use the 30° cutting tool to cut the
top edge of the valve seat. If necessary, use the 45° cutting tool to center the area of contact and set its width.
30°
90-8M0065421 NOVEMBER 2012
a - Rough surface of valve seat
a
20954
a -
30°
20976
a - Previous contact width
60°
20977
o
60
20979
a
20980
Previous contact width
a - Previous contact width
a - Previous contact width
Powerhead
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