Mercury Force 9.9, 15HP Outboards Service Manual, Page 162Get this manual
c REMOVING GEAR HOUSING
WARNING Always disconnect spark plug leads before working on engine 1Drain gear housing
Remove drain plug and washer (Al from starboard side of gear housingRemove vent screw and washer (9) ,
Drain gear housi ng lube into suitable container, oz(0.15 L) capacity or greater