Mercury Force 9.9, 15HP Outboards Service Manual, Page 181Get this manual
78 Install bevel pinion gear (A) Install thrust washer (8) and rear bevel gear (e)Install upper gear housing to lower gear housing Apply sealant (Special Tool NoFT -8983) to both sides of new gasket (A)Install gasket on lower gear housing Position upper gear housing on lower gear housing by aligning spring pin (8) with opening in upper gear housing