Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 296Get this manual
IMPORTANT: The appearance of the forward and reverse gear is almost identicalThere are two ways to distinguish between the reverse gear and forward gears The reverse gear has shorter hub and it has groove cut into the back of the gear just inside the thrust bearing race surfacePress the bearing adaptor into the gear housing using the installation tool as follows:
IMPORTANT: Be sure that the bearing adaptor is positioned as straight as possible to avoid cocking it in the bore while pressing it inaLubricate the threads of the installation tool with Special Lubricant 101 (9213872A1)