1988 Johnson Evinrude "CC" 9.9 thru 30 Service Manual, P/N 507660, Page 197Get this manual
Note I'f anycylinder is outsid.e these tolerances, it must be bored
oversizeOne 0.030 m(0,762 mm) oversize piston is available for this engine To determine oversize bore, add 0.030 in(0,762 mm) to the standard boreRefer to Engine Specifications, Section 1It is permissible to have one or more oversize pistons in an engine
4119Measure the piston diameter 90 to wrist pin hole centerline (major diameter), Va to in(3,2 to 6,4 mm) above bottom
edge of the piston skirt The major diameter for standard size piston at the skirt should not be less than 2.9940 in(76,05 mm); 3.0240 in(76,81 mm) for an oversize piston Measure the piston several more times; Va to V4 in(3,2 to 6,4 mm) above the bottom edge of the piston skirtNone of these dimensions should exceed the major diameter that you measured in above stepAlso, these dimensions should not be smaller than the first dimension by more than 0.0045 in(0,014 mm) 1411
If the grooves on the sides of the piston are worn smooth