1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 150Get this manual
S Use bristle brush and carbon remover solution to remove carbon from side surfacesS tool can be made for cleaning the inner diameter of the tapered ring groovesThe tool can be made from broken tapered piston ring with the side taper removed to enable inside edge of the ring to reach the inside diameter of the grooveCarefully scrape the carbon from inner diameter of ring groovesCare must be taken not to damage the grooves by scratching the surfaces of the groovesMEASURING PISTON SKIRT Measure piston skirt at right angle (90_) to piston pin centerline, 0.50 in(12.7mm) up from bottom edge of skirt Crankshaft
S Inspect crankshaft to drive shaft splines for wear(Replace crankshaft, if necessary Check crankshaft for straightnessTotal maximum runout for crankshaft is 0.006 (0.152mm)Replace as necessaryS Inspect crankshaft oil seal surfacesSealing surfaces must not be grooved, pitted or scratched(Replace as necessary Check all crankshaft bearing surfaces for rust, water marks, chatter marks, uneven wear andor overheating(Refer to "Connecting Rods) If necessary, clean crankshaft surfaces with crocus cloth as shown