I have a 24 foot Harris Floteboat with a 1995 Evinrude 90HP. Guessing boat around 3000 lbs. Prop on it now is a 14x13 aluminum. WOT on the tach is only 4000 rpm. GPS speed showed 19 to 20 mph. Lakes here are all 6000 to 7500 feet above sea level. From what I've read two inches is the recommended change so that would be a 14x11. My question is that enough? The next thing I see is a 14x9 is this one too much. Thanks in advance.