Boats that are super efficient (cats and lightweight V's) can benefit from a lower gear ratio (1.36) sometimes. It's not a science, it's more trial from what I have experienced.

For instance, early 1990's Fountain I used to work on had 1.50 bravos.... flat bottom boat... With 29" Mirage plus and 1.50 gear ratio the boat ran a best of 91 mph and 88 mph with 28" Hydromotives. Same boat, same power, with 1.36 drives ran a best of 84 mph with 27 Mirage plus and 83 mph with 26" hydromotives.

panther my buddy got his boat from the dealer 136drive with a 502 runnig a 23mirage prop top out at 4800rpm . at this time i had 454 30 over dart intake 420 cam ,ss headers 850holley carb and head work i ran 4800rpm my boat was not in the power band .his boat beat me. i change my prop to a 21 pitch and the rpm went to 5200 . i gain 4.7 mph at this time my boat did 66.3mpg . then i put my 540 dart motor in ,now i am over 80 at 5500rpm . all i am saying is he can keep the 136 and make them work with out spending for money if you prop your boat to the rigth rpm it will work . . here a nother one my buddy has a 25 baja 540 procharger with 150 drive has a 30pitch prop doing 78mph at 5200rpm gps i am doing 5400rpm at 80mph with a 23 pitch prop.. gps . good luck with your project i hope what every you do works out for you have a great summer:boat:

Your boat may be light enough and small enough to overcome the torque needed to turn a 1.36, and/or your hull design may benefit from higher propeller speed, hence it's faster...

But, the poster has a 38' Formula...

I agree he doesn't "have" to change anything but the only way he will find out wich one is better is by finding other Formula owners who have done it or testing it himself! Like I said, it's not science and what you or I experience, he may not experience! :)