1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 149Get this manual
3Clean mating surfaces of crankcase cover and intake manifoldInstall new gaskets4Install intake manifoldreed block assemblies to crankcase coverRefer to PAGE 4A-6 for torque specification and tightening sequence5Install carburetorsTorque carburetor (AIR BOX) stud nuts to 100 lbin(11.3 Nm)6Carburetors MUST BE SYNCHRONIZEDRefer to SECTION 2C for proper procedures7Reinstall air box cover8Reinstall top cowling CLEANING PISTON RING GROOVES IMPORTANT: The piston rings are half-keystone rings (tapered on the top side)follow cleaning and inspection carefully! Chromed ring is installed on top
Piston and Piston Rings
IMPORTANT: If engine was submerged while engine was running, piston pin and connecting rod may be bentIf piston pin is bent, piston must be replacedPiston pins are not sold separately because of matched fit into pistonIf piston pin is bent, connecting rod must be checked for straightness (refer to "Connecting Rods" for checking straightness)S Inspect piston for scoring and excessive piston skirt wearS Check tightness of piston ring locating pinsLocating pins must be tightS Thoroughly clean pistonsCarefully remove carbon deposits, with soft wire brush or carbon remover solutionDO NOT burr or round off machined edgesS Inspect piston grooves for wear and carbon accumulationIf necessary, scrape carbon from piston ring grooves being careful not to scratch sides of groovesRefer to procedure for cleaning piston ring grooves