Single engine 450hp 3600 lbs deep v 21' bow rider
Switching from 1.5 ratio bravo 1 with 21p to bravo 3 with 2.0 ratio.
I want strong holeshot.
I just bought the b3 and it did not come with any propellers.
What would be a good set of props to get a baseline?

26 or 28...sounds like you were already a little on the low number end with the 21p and 450hp. You will have a great holeshot either way. Make sure the B3 trim limiters are utilized. I just swapped an old B3 on my boat last summer out of curiosity and I doubt that I'll ever put the B1 back on. Then again, I'm only running a stock 502 Mag (415HP) so I lost really nothing top. On most 65mph-ish boats, its going to be all positives. The only small negative that I have is a little looser handling a higher speeds...the B3 will lift the stern more than almost any single prop.

I'm betting you will be able to turn 3 x 3 28's no problem. I turn 26's with the same ratio on 375 HP in a 26' vee.

Your correct about the 21p not being enough. The 450hp engine is new. The 21p was used with the old 330hp.
So you guys are thinking 3x3 28's?

Call Brett at Bblades and tell him what you have and he will tell you where to start and you can also use his test prop service to make sure you get the right set before purchasing. What is the engine's max RPM?

Engine has not yet been assembled much less installed. Its a 496 with 9.7 cr RHS 320cc rec port heads and zz502 cam. Figure 5700rpm?

I'd wait on props until you know what your HP/RPM number is. I'd invest in a dyno session if it is not already in the cards. $500 well spent.

Yes no rush on props. Was trying to get ahead of things.

You might get more responses if you post in the prop section.