1975 Evinrude 40 HP Outboards Service Manual, PN 5093, Page 53Get 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 all forms of grit are removed before assemblyWork in clean surroundings and with reasonably clean handsCoat all bearing surfaces, cylinder walls, etc with clean oil before assemblyWhere the use of "oil" is specified, we ecommend OMC Outboard Lubricant
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 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 expanddReplace retaining rings, lettered side out, 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 5-20INTAKE SIDE OF DEFLECTOR