MONSTAAA
Nice pic of your boat
I think i may have wet myself a little.
WOW

hi i have 1988 240 136 gears 21 mirage lab 70 mph at 5200rpm my buddy has same boat has150 gears 25 mirage68mph same power i run 3000rpm 40mph i crus 3600 rpm doing 55running on 2 barrell good on gas

You will get better fuel economy and throttle response with a 1.50 ratio drive IMHO. Give your manufacturer a call, they can probably best tell you what will work....

Al boats are different..... some boats tend to gain speed with a lower gear ratio (Cats, lighter V's etc.) because they can overcome the torque load while others actually loose speed.

Here's a few boats I set up in the past along with my results.....

My own boat - 36' Apache: 1.50 ratio with 32" Bravo I's ran 83 @ 5100 rpms (GPS). Switched to 1.30 (Bmax - larger gears - more recipricating mass) and 26" Bravo I's and the speed was 81mph GPS. Also, with 1.50 RPMS went straight up to 5100, with the 1.30 RPMS would go to 49-5000, then creep up to 5100.

42' Fountain, flat bottom, triples. 1.50 gears, 27" Mirage Plus to 5600 rpms boat ran 88 mph. 1.36 gears and 25" Mirage Plus' boat ran 83 mph, boat was a dog.

29 Velocity. (don't remember prop sizes but they were Hydromotive's)... 1.50 gear ratio boat ran 72 mph. 1.36 boat ran 76 mph.

there are numerous combinations available so that the boat can actually run very similarly with either 1.5 or 1.36...prop selection would be the key...each boat is different, so the combination of gears and props is a trial by error equation......figure out the rpm range you mostly run in, (not everyone runs at WOT all the time), what type water you mostly run (flat or rough), then decide what prop/gear combination you can maximize........not an easy answer to your question