1989 Johnson Evinrude "CE" 9.9 thru 30 Service Manual, P/N 507754, Page 145Get this manual
If any cylinder is outside these tolerances, it must be bored oversizeOne oversize piston is available for this engine (0.030 in 0,762 mm)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 1201 9Measure the piston in two locations, 90 apart from each other, Va in(3 mm) above the bottom of the piston skirt10The difference between the two measurements is the outof-roundness and must be no more than 0.002 in(0,05 mm)11Refer to Engine Specifications in Section for piston dimensions