Cylinder Head Reassembly; Valve Installation - Mercury 25 EFI Service Manual

Cylinder Head
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°
12. If the valve seat contact area is too narrow and situated near the bottom of the valve face, use the 60° cutting tool to cut
the bottom edge of the valve seat. If necessary, use the 45° cutting tool to center the area of contact and set its width.
a

Cylinder Head Reassembly

Valve Installation

NOTE: Valve seals are color coded to ensure they are installed onto the proper valve guide. The black valve seal is for the
intake. The green valve seal is for the exhaust.
Page 4B-16
a - Previous contact width
60°
20977
o
60
20979
a
20980
a - Previous contact width
60°
20981
© 2016 Mercury Marine
a - Previous contact width
a - Previous contact width
90-8M0105568 eng MARCH 2016