Mercury Mariner Outboards 2.2 / 2.5 / 3.0 Service Shop Manual, Page 48Get this manual
Install bearing retainers (a) into cylinder block Check piston ring for spring tension thru exhaust port by pressing with screwdriver as shown If no tension exists (ring fails to return to position) it is likely that the ring was broken during installation and mus be replaced
Install crankshaft assembly into cylinder block as follows: aLubricate piston ring, piston and cylinder well with light oilbAlign ends of piston ring with locating pin as shownNOTE: Ring Compressor is not used to install piston into cylindercKeeping crankshaft horizontal, push piston into cylinderGently push crankshaft down into positionRotate bearings so that alignment pins (a) are positioned into notchesPosition oil seals against retainers