Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 298Get this manual
Gear LocationBacklashes Checking and Adjustment Reverse Gear
INSTALLATION (FOR CHECKING BACKLASH ONLY)
IMPORTANT: The appearance of the forward and reverse gear is almost identicalThere are two ways to distinguish between the reverse gear and forward gearThe reverse gear has shorter hub and it has groove cut into the back of the gear just inside the thrust bearing race surface
1Lubricate the large reverse gear thrust bearing with
Quicksilver Gear Lubricant (92- 13783A24) and position first the thrust race, then the bearing into the gear housing and onto the reverse gear bearing adaptor