Looking for input...Currently running a 330 HP 7.4L with a Bravo 1, Mercury Rev 4 21P. That pulls to 4300 RPM and 53 MPH light load, heavy chop. Upgrading engine this winter to a 450 HP 540Mag Bravo 4V. The Rev4 has been a great upgrade to the stock Mirage 3 blade, but I'm thinking too small behind the 540. Anyone have a similar set up?

me and my buddy both run Rev 4 25 pitch, 5,400 rpm. Formula 242's

Appreciate the feedback. What are you running for power though? WOT range on this particular engine is 4200-4600. But it is 560 ft lbs torque. There's a 26P Rev 4 on ebay but I'm thinking that may be too steep. Prop calculators I've played with are coming up in the 24-25 range.

About the same I have a healthy 509 and he has a strong 540. you can't go wrong with that 25 pitch starting point.

How far are you on your engine? Any interest in buying a recent professional built marine low hour 500ish hp 509?
Saves time, frustration and money. DM me if interested (still in my boat)

Go the Mirage Plus in a 23 to start. You are most likely going to spin the 540 a lot harder than your old 454. I had a 242 with a 550 hp 427 that I spun to 6200 RPMS. I only used a 21 pitch Mirage Plus! The exact same prop as I used with a stock 454. However the extra RPM got me up to 68 MPH. A 540 is going to have a lot more torque but I'm pretty sure 25 P will be way too much, start with 23 and go from there.

What is your target max rpm and speed?

It's only rated to 4200-4600RPM from Mercury. To make that few HP from a 540 they made it a very conservative build. I believe stamped rockers.
I'd start with your prop to baseline. It's only a little more than 100+ more HP and a bunch more torque. I believe you should be around 25P.

I missed post #3. Reading that, I agree with you.

I have a Mirage+ 25 BBlades tuned prop that has never been run if you are interested. Still bolted to the original shipping plywood.