I have a twist. My first engine was a os 46 ax with a 12.25 x 3.75 and that was plenty of power. Plenty wasn't enough and I put in a ys .63 If you can't affors the saito, I guess that rules out the ys but it is incredible! If you are trying to save $, the os 46 ax, 50 sx, enya 50 cx or super tigre 51