I have a 55AX in my WM CAP232. Tried the 12.25x3.75 and a 13x4W and now a 12x7, seems happiest on the latter prop, but may try a 13x4 normal. On the flat pitched props seems to hang a bit when going down to idle and runs a little rough in the mid range, again not as sweet as my YS63 on a 13x4W but still pretty pleased with it so far.