Kelsey, my reading of the chassis illustration for model 330413 is that there is no component inboard of the engine shaft pulley until you get to the other side of the mower's sideplate - the next component is No. 37, the Engine Shaft Washer. The point is that on the illustration it is on the inboard side of the side-plate, not the outboard side. On your mower it is on the outboard side, with a large nut that I haven't found on the illustration so far.
