You can add tape to the crank. The two Brison 3.2 have smaller shafts (I think 3/8th inch versus 10mm) so the only way was to add tape. Never gave me a lick of problems on either one and that is a single bolt for the prop. I used blue painters tape. Nice and easy to get off when you wanted to.

When Gary ahd Brison he gave a plastic sleeve to make up for the difference but I lost mine on both engines. A clear plasti sleeve in 2 inches of grass is awfully hard to find, especially if it's a bit windy