1978 Johnson 4HP outboards Service Manual, Page 60Get this manual
kIf necessary to remove pistons from connecting rod, remove wrist pin retaining rings, using needle-nose pliersSee Figure 5-9Drive wrist pin through to free piston from connecting rod See Figure 5-10 NOTE
One side of piston is marked "Lon insideWhen wrist pin is to be removed, "L" side of piston must be up and driving tool must be applied to loose endBe careful not to distort pistonSee Figure 5-11
Figure 5-11"L" Mark on Piston
CLEANING, INSPECTION, AND REPAIR
CYLINDER BLOCK AND CRANKCASE Check cylinder walls for excessive wear and check cylinder ports for carbon accumulation Cylinder walls wear in various degrees depending on lubrication and conditions under which the motor is operated Major portion of wear is in the port area and the area covered by ring travel8 30 33
Figure 5-9Removing Retaining Rings
Check cylinder for size and wall straightness by using an inside micrometer or dial bore indicatorRefer to Section for specified dimensionsIf wear is greater than 0.002" (0 .05 mm)replace cylinder block or rebore block for oversize pistonsPiston and ring sets are available 0.030" (0.76 mm) oversize