Using the prop slip calculator on the blades site my slippage is close to 24%. I have a 1999 donzi 26zx with a 1.50 bravo drive,26p bravo prop and I'm turning 5500rpm running 70 mph. I feel like the motor can handle a 28p bravo one,but not sure if that's what it will take to decrease the slippage issue. Not sure what my X is, but I've been told that it's pretty high. The motor is a 516 with roller valve train, dart pro 1 heads, and an 850 carb. Should make 550-575hp. Anyone out there with a similar setup have some advice? Also, I don't even want to turn 5500rpms, 5100-5200 is where I want to be.

I'm thinking unless you have a very mild cam your making a bit more power than you think. Sick stinger has a 28 zx with a -2 short lower and a 500hp. He's going just over 70 at 5100 rpm. I had a 510" motor with dart pro 1 325's making over 620hp easily. Spun a 26 to 5500 in a 24' baja at 78mph. I say try the 28 and double check your slip. Keep in mind a bravo 1 prop is about 1" less pitch than advertised.

I have a 1999 26zx with still the 200 hour 502mpi. Eddie marine manifolds, long risers, and no mufflers. Bravo 1.5 ratio. I spin a 25p revolution4 prop to 5000-5100 rpm at 69.5 gps pretty consistantly with 2-3 adults and 1/2 or less fuel. We hit 70.5 this weekend at the River Shiver (47 degrees). Yes the x I have been told is pretty high on these hulls. Prop is stock with a little cup added. My only complaint with the revolution 4 is that if I dont watch it I can blow it out getting up on plane as the bow starts to settle down.

Any reason why you are against spinning 5500 rpm? Your engine should still be making power there with those heads, assuming you have a could cam and intake match.

Get the slip down but might I suggest don't be afraid to spin those rpms. Leaving your set up unloaded is good for that drive on such a big single engine with big hp. Think of your truck going down a level road wide open, then think I going up a hill wide open. Loading your engine back down to 5000 puts a big load on everything.

X 2

Also when calculating slip for Bravo 1 props, reduce the pitch by 1" of what is actually stamped on them.

is yours white with yellow and purple stripes?

Go with a labbed 30 pitch,,that will put you where you want to be..

No white with red stripes. There is one on the chain "purple haze" that blew the hatches off mine on Grass lake. No way he is running stock power. Maybe procharger or blue motor.

Mrfixxall, my boat has a black stripe that fades to checkers. It used to belong to zxxx and has been over 100mph.
Lilred, the cam is mild at 547 lift on both sides, and my "x" is 6 inches. I'm gonna try a 28 that a friend has just to get some more info and then call bblades and start testing props.

6 inches is not an X dim. That may be your propshaft amount below the bottom. If so, that is pretty deep.
BTW, that cam is a dog for a 516ci with those heads. That cam is barely an upgrade for a 454 mag. No way you are making 550-575hp with it. More like 475hp.