Mercury Mariner 4, 5 102CC Sail 1990 Outboard Service Shop Manual, Page 18Get this manual
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Ignition Timing TOC Timing Mark Alignment
1 Co nnect im ing lig ht (91-99379) to engi ne2 Start engi ne and all ow it to wa rm up to no rmal operating temperatu re3 Th rottleengi ne back to idle