1977 Evinrude 4HP Outboards Service Manual, PN 5303, Page 49Get this manual
Figure 5-9Removing Retaining Rings 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 accumulationCylinder walls wear in various degrees depending on lubrication and conditions under which the motor is
operatedMajor portion of wear is in the port area and the area covered by ring travelCheck cylinder for size and wall straightness by using an inside micrometer or dial bore indicatorRefer to Section for specified dimensionsIf wear is greater than .002" (0.05 mm), replace cylinder block or rebore block for oversize pistonsPiston and ring sets are available .030" (0.762 mm) oversizeONaTE
If your shop is not equipped to rebore cyl-