Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 314Get this manual
3 Place the thrust race on top of the thrust bearing with the stepped side against the thrust bearingInstall the forward gear bearing adaptor using hook tool (which was fashioned when the adaptor was removed) as shownEnsure that the adaptor seats even Iy against the thrust race -Gh
50785 Thrusl Race
Use the Forward Gear Installation Tool (91 -8 15850) to install the forward gear down over the propeller shaftEnsure that the thrust race seats evenly onto the shimTap the race down lightly using soft punchDo not damage the thrust race surface