Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 73Get this manual
TIMING AND SYNCHRONIZATION
Ignition Timing
Toe Timing Mark Alignment
IMPORTANT: As this ignition system is fixed, no adjustment to ignition timing is possiblelf ignition timing is not within specifications, refer toTest Procedures" following 10 locale faully componenl(s)1Remove spark plug2Install dial indicator through spark plug opening in cylinder head
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