You have the incorrect hardware. You need to get the right stuff. Its been a while since I played with those bravo style props, but if I remember correctly, they had

Old style, which was a solid hub setup, just larger than the shaft opening, with three connecting points to the prop. They used a small tapered thrust washer.

Then they had the flo torq style I believe, which took a much larger diameter thrust washer, with a different hub insert that has 4 keyways that slide into the hub (behind prop nut).

Someone else might be able to explain it better

This sounds right, my original prop had a hub that was basically just a little bit bigger than the shaft size. It has a small maybe 1/2 inch depth tapered thrust washer. The prop I am trying to use as a backup has a much larger hub. I believe they are both solid hubs.