RE: TT 91 FS
Usually, the propeller drive washer will rest against the center of the front bearing. A thrust washer isn't usually needed, but it depends upon the engine. The front end of the engine is lubricated by oil in the fuel that is pressure-driven forward through the main bearing. If your fuel doesn't have enough oil content, then little oil will get through to the front of the engine. That could contribute to your deteriorating front bearing.