A boat propeller the pitch of whose blades can be controlled while under way. That much is fairly obvious, but more careful observation reveals that most VP props are also reversible, with the range of pitch extending from coarse ahead to coarse astern. An extension of the idea is the VP prop which also feathers, in that the blade pitch goes beyond any usefully propulsive angle to the point where the blades are edge-on to the water flow and the drag while sailing is minimised. The conventional VP and reversing prop turns always in the same direction, requires no reverse gearbox, and should permit fine control of thrust by varying blade pitch without changing the throttle setting.