1971 Johnson 125HP outboards Service Manual, Page 57Get this manual
NOTE Always use new gaskets throughout when reassembling the power headPISTONS, WRIST PINS, AND CONNECTING RODS aThe difference between port and starboard cylinders must be considered when assembling pistons to rodsPistons must be installed in cylinders with intake side of deflectoI: toward intake portOil hole in connecting rod must be toward top of motorSee Figures 5-29 and 5-31bApply coat of oil to wrist pin, making sure surface is cleana drop or two of oil in each pin hole in the pistonPlace
One of the piston bosses is bored for slip fit on the wrist pin and the other for press fitWhen installing the wrist pin, drive from the side marked "LOOSE", using fixture to guard against distortion or damage during the operationcInsert wrist pin through slip fit side of pistonOil wrisL pin bearing in connecting rodPlace connecting rod in position, then proceed to drive or press the pin into pistonSee inset, Figure 5-29This can be accomplished more easily if the piston is heated slightly, causing it to expanddReplace retaining rings, making certain they come to rest securely in the groove provided for this purposeeCheck piston with micrometer to determine whether piston has been distorted during assemblySee Figure 5-30If slightly out-of-round, tap high side with light mallet (DO NOT use hammer) to restore original roundnessProceed carefully and caliper frequently until the piston is rounded out