Hi,

28 x 10 seems to be the right prop. It will turn a 30 x 10 but it really lugs the engine (mid 5000 range)

RPMS for a 28 x 10 should be in the 6000-6500 range.

the 120 is rated at slightly more hp than the newer 3w 110 but if propped for the torque, it will out perform the 110.

hope this helps

Elson