Clamp on Prop Protector suits 22 mm shaft - 80 mm diamter Blade.

22mm BORE CLAMP-ON PROP PROTECTOR 80mm DIAMETER BLADE 
 
Supplied as an assembly that is split into two halves along the longitudinal axis so that it can be installed on the shaft without removing the propeller. The width is 17 mm (0.67"). A gap of 23 mm (0.7") is sufficient; this includes 6mm (1/4") of space for water to circulate to the shaft bearing. It is clamped onto the shaft by two Allen screws and is also fixed by a set screw that locates into a small drill dimple made in the shaft. This type is available for shafts of 20mm (3/4") dia. up to 40mm (1 5/8").