I have a stock 502 w/ 435 hp, stock Bravo drive and Hydromotive LH 22". Getting about 5000-51000 rpms WOT and mid-upper 60s. I tried a Bravo 23 RH and it made the boat porpoise quite a bit. Not sure how everyone is running larger props and getting into the 70s...

I would be happy with 65mph,,,,,,,,,,,,,,,,,,,,,,,

How many HP does your 509 have?

If you have the weight on your boat and propshaft HP and choose the Heavy V bottom in this calculator
You can aprox see what kind of speed you are suppose to get

http://www.go-fast.com/boat_speed_predictions.htm

93 27' with a 502mag with the 500 efi cam and valve train, 24 lh hydro the best I get is 67 and I can feel it slipping, lh bravo1 24" and I get about 71 and a better mid range acceleration and planing.....stick with what you got I don't think you can improve on that

Bigger props, lower gear ratio. Stock 496 mag ho's have a little more power than the stock 502's
I have a 496 mag ho w/ bravo 1X drive 1.65-1 ratio. 5000 RPM 5100 on a cool day 68-70 MPH with a bravo LH 30P
When it is really hot best I can get is 4800RPM
1.5-1 ratio would be the same running a 28p bravo.

Just to add My drive is a 1.36, dyno sheet 701hp@5400, 715tq@4750