1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 157Get this manual
3Align piston ring end gaps with ring locating pins as shownCheck locating pins making sure they are tight Check rings by viewing through exhaust ports while depressing rings with screwdriverIf no spring tension is there (ring fails to "spring" back), the ring is probably broken and must be replaced, NOW, before installing the crankshaft
Crankshaft Installation
51082Locating PinPiston Rings
4Remove connecting rod cap from connecting rod being installed5Install each piston with "UP" identification facing flywheel endPistons MUST be installed in this directionUP
S If Lower Bearing and Gear were removed from crankshaft, reassemble using arbor press and suitable mandrel for bearing; gear slides on(NOTE keyway and key in gear to crankshaft assembly Install main bearing retaining ring after pressing main bearing tight against the oil gear