Mercury Force 9.9, 15HP Outboards Service Manual, Page 183Get this manual
GPRESSURE TESTING GEAR HOUSING 1Remove screw and washer from lowe r
starboard side of gear housing
Thread adapter of pressu re lester (Special Tool No FT -8950) into drain hole and tighten securely
NOTE: Make sure ven screw is securely tig htened
IMPORTANT Seals may be damaged if pressure exceeds 10 PSI3Pressurize hous ing to 10 PSI and obse rve gauge for five minutesIf pressure drops, immerse housing in water and repressurize (10 PSI)Rep lace seals wherever air bubbles appear, then retest