BlackJack/250 SHO High Performance Prop?

[BaseballFisherman]

I'm currently running a BlackJack with a 250 SHO. It is turning a 21 pitch saltwater series 2 prop. I'm seeing 40 mph at 4000 rpm cruising with any load and I'm getting around 63 mph WOT running regular octane gasoline and a light load (1 person, fishing gear, and 1/4 tank of fuel). I'm satisfied with the performance im getting but I've been reading forums about guys running the same boat/motor at 65-68 mph. I'm calling BS but maybe they know something I don't? I know the new 300 Offshore Yammy (same power block as the SHO) is running right around 70 mph on this rig so 68 with a 250 SHO seems a little far fetched to me. I assume they had to be running premium fuel, which I have noticed will run slightly faster in my rig, and with only a couple gallons in the tank. I've been told that running a Bravo 1 XS prop instead of the saltwater series 2 may increase performance but I am no expert when it comes to props. The SHO runs great on my BJ with the saltwater series 2 but if these guys aren't full of crap about their performance numbers, I'd be extatic to squeeze a few more mph out of my rig. If there are any prop gurus lurking or if anyone here has experience with the SHO and different props, I'd appreciate your insight as I don't have much experience playing with props. All I'm looking to do is maximize the performance and efficiency of my rig if there is a better prop out there than the one I already have.