1974 Johnson 40 HP Outboard Motors Service manual, Page 52Get this manual
REASSEMBLY OF POWER HEAD Proceed slowlyMake no forced assemblies unless press fits are called for and make no "dry" assembliesBe sure all parts to be assembled are clean and free from dirt and gritPerfectly good cylinder walls, pistons and rings can be ruined in few minutes of operation unless aU forms of grit are removed before assemblyWork ip clean surroundings and with reasonably clean handsCoat all bearing surfaces, cylinder walls, etc with clean oil before assembly
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 markedLOOSE," using fixture to guard against distortion or damage during the operationSee Figure 5- 16cInsert wrist pin through hole in loose side of pistonOil wrist pin bearing in connecting rodPlace connecting rod in position, then proceed to install the wrist pinThis can be done more easily if the piston is heated slightly, causing it to expand dReplace retaining rings, lettered side out, making certain they come to rest securely in the groove provided for this purposee Check piston with micrometer to determine whether piston has been distorted during assemblySee Figure 5-20