Mercury Force 9.9, 15HP Outboards Service Manual, Page 144Get this manual
13Center punch two places at bottom of cylinder assembly Position punch 180 apart and 1116 in(1.58 mm) from edge of seal boreRemove old punch marks with bearing scraper or other sharp tooli
NOTE: Impressions should be minimum of 18" (3.17 mm) from cylinder to crankcase over parting line and be deep enough to force material over outer edge of seal case minimum of 0.005 in(0.121 mm)