Mercury 5 SERIES Service Manual page 127

4. Check the margin thickness (a) of the valves after the valves have been ground. Any
valve with a margin thickness of less than the specification, should be replaced.
5. Measure valve stem runout, replace if out of specification.
6. After repair of valve seat, lap the valve for proper fitting to valve seat.
7. Apply lapping compound to valve seat and lap valve while turning valve with valve lap-
per.
8. Apply lapping compound in 3 sequences; coarse compound first followed by medium
and then fine compound last.
IMPORTANT: Before using lapping compound of a different grade, completely re-
move previously used compound.
IMPORTANT: After lapping is complete, wash valve and valve seat removing all lap-
ping compound from them.
90-857138R1 MAY 2000
45
a
Margin Thickness "a"
Intake Valve
Exhaust Valve
Valve Stem Runout Limit (Max.)
Intake Valve
Exhaust Valve
55809
0.028 0.047 in. 0.028 - 0.047 in.
(0.7 - 1.2 mm)
55811
0.0006 in. (0.016 mm)
CYLINDER HEAD
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