Do I need to look at a 5 blade?
 

I have a Velocity 280 with a single BBC with about 700hp. I have tried a Hydromotive QIV 27pitch and a labbed Bravo 4 blade 30 pitch. I have a modified B1 with a nose cone, 1.5 ratio and my prop shaft is 4" below my pad. The Hydro breaks out on the slightest throttle getting on plane and will break loose in rough water really bad. The labbed Bravo gets on plane pretty well and will stay connected as long as I don't hit the throttle to hard. I have to watch both props when I get to 3000rpm as the motor is getting into it's powerband and will break both props loose pretty easy. I'm still working out the top end, but the bravo will run 80 at 5000rpm all day with a full tank and 5 guys on board. When I'm by myself and horsing around I can pretty much break the bravo loose on demand from 30-40mph. It's like driving my supercharged Corvette when the tires are cold. Any suggestions? What do you guys do that are running serious power

I'd definitely try a 5 blade. The other option to try is a 1/2" or 1" drive spacer

Just be aware that the 5 blade "bites" the water harder on re-entry. You have to be better on/off the throttle when the prop is coming out of the water so as that HP/tq you are pumping through that B1 does not tear it apart.

You are 4" below the pad?

Yes, prop centerline is 4" below the stepped pad.

I'm getting ready to test a Max 5 on my Donzi today. Pretty sure the pitch is too small though.

What pitch/diameter?

I might be interested in it, for my Donzi😁