There are two interesting points about this photo of the inboard end of the FPB64 prop shaft.

The first is the length of the engagement for the shaft coupling to the shaft, double the norm. Any idea why?

Second is the shaft brake, about which we have spoken in the past. The brake is there to assist in changing the “drive saver” between transmission and prop shaft.

And the extra length of engagement? The inboard end of the shaft has the same taper as the outboard, so that the shaft can be reversed (the prop will fit on either end) in 10,000 hours or so when there is a bit of wear on the outer end. OK, that is probably ten or fifteen years from launching but it pays to plan ahead.