Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 233Get this manual
13Install the thrust washer and new ball bearing onto the reverse gearPress on the inner race of the ball bearing using the pilot washer until the bearing bottoms out on the gear 15Press the bearing carrier onto the reverse gear and bearing until the bearing bottoms out in bearing carrier, using the pilot washer to press against the carrier
aPilot Washer (PI 91 -36571)Ball BearingThrust HubReverse Gear