1988 Johnson Evinrude "CC" 9.9 thru 30 Service Repair Manual, P/N 507660, Page 39Get this manual
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Gearcase Gear Ratio
Recommended 20,25 28,30 25 CommOL77JC4 0.040 in (1,0 mm) OL78V FIXED GAP UL77V FIXED GAP
Alternate L77JC4 0.040 in(1,0 mm) L78V FIXED GAP NA