I had my boat out for the first time since I put a whipple on it.
I was spinning a 24 4 bbl bravo at about 5150-5200 rpms running around 65.
Now I have the whipple with 5-6 lbs am pushing 233 more hp than before and can only spin a 28 4bbl bravo to 4850.

At 4850 I am at 609 hp at 5375 I am at 658 hp.

Do I need to go to a 26 4bbl to reach my peak power?

And why would I only go up to a 26 with 233 more hp?

In your case it takes about 20 hp per mph. With 200 additional hp I would expect you to run in the high 70's.

A 26 Bravo 1 would run about 5400 in the mid to high 70's.

Some prop work could get the 28 in the low 5000 range with an increase in speed due to both the prop work and the additional hp the motor will produce at the higher rpm.

A 26 Bravo 1 will put you back in the same rpm range you were in before the upgrade. This makes complete sense for the hull and hp gain you induced. A conservative Lab on the 26 should get you in the hp range you need to be in and into the 70's.

put a shorty on it, and lab a 28.