Prop selection for Formula 242
 

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.

Engine he is referring to Genuine Mercury Marine parts, large inventory, fast shipping. Mercury-Mercruiser 8M0085999 540 MAG BRAVO 4V Genuine factory part

Rev limiter should be set around 4750 rpms.

I have a REV 4 23 pitch 4 blade for sale, very nice condition