I have a 99 25ft Colbalt with 454 mag mpi. I currently have a bravo 3 with 28 pitch prop. My maxed RPM is 4800 at 56mph. Would I be better off with a 24 or 26 prop to reach a higher rpm and speed?

I think you are there . Max rpm for a mpi 454 is 4800 or real close . If it's not broke just enjoy it .

If you are woried about top speed swap out the Bravo 3 for a Bravo 1 lower. Or just leave it alone

I run 28p on my Bravo 3 driven Baja 272. I've seen 61mph (GPS), bone stock engine. Not sure of the RPM though. I have another set of 26s, and not a huge difference.

Don't change your B3, one of the best drives out there for a boat like that.

You should be turning 5K RPM at WOT with a 454 MAG MPI. You can have Brett at BBlades work those 28's to gain more RPM and top speed.

+1

According to my Cobalt manual you should be using a 26P propset for
your Bravo 3 with a 454 Mag MPI. The 502 Mag MPI used the 28P
propsets. This is for the 252/253/25LS models. Which do you have?

Also you really need to get an accurate tachometer, digital is best,
before you do any more "testing" or make any changes. I went
through this myself and found significant speed increases with the
last 250 RPM's.

I know the bravo 3 is faster than the bravo one up to 63 mph so I don't think my boat will be breaking this speed with my current stock 454 mag mpi. Im just trying to get close to the max speed performance of my outdrive.

Yes BBlades is on my list. Also I thought that I had 28 props on my drive. It turns out they are 24. Must have been having one of those days when I checked em out.

I noticed on the rear prop, on the outer rim has a flat spot and is not totally round. I would guess this is whats causing my vibration when my boat has a load of people full cooler and tank of gass.

I have 24 props.