Ron,
I ordered the 16.5 X 11 for the same reason you did. I liked the 16.5 x 13 for reverse maneuverability,but couldn’t get to max engine rpm. Itwas certainly better than the fixed prop that came with the boat, and you didn’t have to live with a freewheeling prop. Just having a folding prop. gave me a 1/2 To 1knot in added speed when sailing.Because my boat has the 2GM20F, i was having to throttle back to avoid fogging the mosquitos at full open. I think it also makes a difference as to which transmission is behind the engine.