The old Volvo Penta Aquamatic drives (pre-1994) used a cone system to secure either a long hub or a short hub propeller. We get a lot of questions and confusion about what cone goes with what propeller series. Today I was talking to Rick Myrick of RNR Marine in Bradenton about a customer situation and provided the attached picture and the following explanation.
The long hub propeller uses the cone in the middle, which sits down in the propeller. An allen head bolt runs down through the cone into the prop shaft to secure the cone and keep the propeller in place.
The short hub propeller uses a longer cone--either the one on the right, or the combination of the cone in the middle and the spacer on the left, which makes an assembly that looks like the one on the right. The cone is secured by either the aforementioned bolt, or a tab washer that bends into the serrations in the cone (or spacer).
Of all the drives, the Volvo Penta seems to lose props most often. Main culprit seems to be the bolt coming loose. Using a little Loctite will keep the cone and prop in place.