1975 Johnson 4HP 4R75, 4W75 Outboards Service Manual, Page 41Get this manual
Figure 5-9Removing Retaining Rings 306 4
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", replace cylinder block or rebore block for oversize pistonsPiston and ring sets are available .030" ove rsizer lfrlNOTE