Parts such as the Lower Drive 2: Propeller (pa 3x11-3/4"x9-1/4", Ybs40-5 Nut,nylon, Cover, Water Inlet 2, Nut, Castle(6g8) are included in the T9.9(eh/er)p 1991 Lower Drive 2 parts fiche.
On this parts fiche the Bolt (j40) is the most specified component.
The Yamaha LOWER DRIVE 2 has twenty-five products enlisted in the schematic.