The 14 1/4 diameter is mainly for the larger V6 style gearcases and the 13 & 13 1/4 is for the smaller V4 / inline style cases. Putting a smaller diameter prop on a large gearcase will most likely increase venting.
You'll find that the Hub of the 13" prop is Only 4".......<br /><br />The 14 1/4" prop will have a Hub Diameter of 4, 1/2".........<br /><br />And it'll Ventilate Real Bad,... Like Dhadley says.........