Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 239Get this manual
CYLINDER BLOCKCRANK CASE
2Remove top and second ring3Remove oil ring (bottom rail, top rail, and scraper)NOTE: Use piston ring expander tool (PIN 1-24697) to prevent rings from breakingIf reusing rings mark their location (piston #1#2, or #3) for correct installation