I have heard that before and the only one I heard of was older Johnson and Evinrude's getting boosted from 9.9 to 15 hp by a carb change. Many lakes passed laws of a max HP of less then 10 and manufacturers just started to rate their 10's at 9.9 so people got around that by taking a 9.9 and boosting it to 15 by using a bigger carb. Not sure cause it was just a rumor, but I heard that law was aimed at the Mercury Super Hurricane 10
