1985 Mercury Outboard V-300 V-3.4L Shop Service Manual, Page 109Get this manual
Pistons and Piston Rings IMPORTANT: If engine wa submerged while engine warunningpiston pin 8nd orco"nectlng rod may be bentIf piston pin Ibent, piston mUI' be
2Check tightness of pi ston ring locating pins Locating pins must he tigh!3Thoroughly clean pistonsCarefu ll remove carbon deposits (rom pi stonswith soft .ire brush or carbon re mover 50lulion Do nol burr or round off machined edgesInspect pi ston ring grooves fo wear and carbon accumu la ti onJr necessaryscrape carbon from pi ston ring grooves being carefu not to scratch sides of groovesRerer to procedure follow ing for cleaning piston ri ng grooves
replaced (PI,ton pins are not lold leperately be-
cause of matched tit Into piston If plslon pin I, bent, connecting rod mUlt be checked for stralghtne (refer toConnecting Rods", following, for
checking ,'ralghtnell)IInspect pi stons fo scoring and excess; ve pisto skirt wear
Cleaning piston ring grooves
NO TE: Cleaning in.sfru lions differ between the rectangular ring groove and keystone (tapered) ring groovePiSlons may halle two keystone ring grooves or one keystone ring groove and one rectangular ring groove as shownRectangular ring groove