1968 Evinrude Big Twin, Big Twin Electric, Lark 40 HP Outboards Service Manual, Page 50Get this manual
CLEANING; INSPECTION, AND REPAIR CYLINDER BLOCK AND CRANKCASE Check cylinder walls for excessive wear and check cylinder ports for carbon accumu1ationCylinder walls wear in various degrees, depending 1ubrication and conditions under which the motor is atedMajor portion of wear is in the port and the covered ring trave1Check cylinder for size and wall straightness using inside micrometerRefer to Section for specified dimensionsRep1ace cylinder block, block for oversize pistons if wear is in excess of .003"Pistons and ring sets available .025" oversizeNOTE