2001 Mercury Mariner 50-60HP Factory Service Manual, Page 275Get this manual
CYLINDER BLOCKCRANKCASE
4Install upper and lower oil seals on crankshaftPosition oil seal lips as shown5If removed, install dowel pins 6Carefully lower crankshaft into placeIMPORTANT: Make sure the lower oil seal notch is positioned into the groove in the crankcase
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aDowel Pin (2)Upper Oil Seal
cLower Oil Seal (Raised Rib)Oil Seal Groove