The problem with the Hughes 29 boats (confirmed by other owners that it's not just mine) is that there is very little clearance between the prop and the shaft housing. On my boat there is only 3/4" clearance. That isn't enough room for a standard shaft mount anode.
After much searching, I found a source for an anode that would work. It is a prop-nut mounted anode. The following are the part number and spec for the anode.
CMPNCC10 - For 1" diameter propeller shaft. Complete set, zinc and bronze nut.
Shaft Size: 1" (25mm)
Length: 3" (76mm)
O.D: 1 7/8" (48mm)
Weight: 1.38 (0.63kg)
Thread Size: ¾"NC10
O.D.: 1 7/8" (48mm)
Fastner: 5/16-18x1 socket head w/patch
These anodes are available online at The Binnacle.