1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 173Get this manual
9Measure the piston diameter in at least two places to verify piston conditionMake your measurements 1 to 1f4 in(3,2 to 6,4 mml above the bottom edge of the piston skirtturersUse the chart below to visually identify the piston you are measuring and select the appropriate dimensions The major diameter of the piston is measured 90 from the wrist pin hole centerlineSee the chart The minor diameter of the piston is measured in line with the wrist pin hole centerlineThe minor diameter must be smaller than the major diameter by the cam dimensionSee the chart
1Note These engines have pistons of several different manufac-