Mercury FourStroke 3.5 - Page 114

Powerhead
90-8M0065421 NOVEMBER 2012 Page 4A-33
7. Start with the 45° cutting tool to clean up any pitting or rough surface of the valve seat.
a - Rough surface of valve seat
8. Use the 30° cutting tool to adjust the contact width of the top edge of the valve seat.
a - Previous contact width
9. Use the 60° cutting tool to adjust the contact width of the bottom edge of the valve seat.
a - Previous contact width
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.
a - Previous contact width
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.
a - Previous contact width
45°
a
20954
30°
a
20976
60°
a
20977
a
30
o
60
o
20979
30°
a
20980