These numbers I hear I not making sense. I am running a 502 stock with a brand new 25 pitch mirage at 4400 rpms the GPS on moderate conditions is about 72 mph. I can't believe that a carburetor change would put a 330 near the speeds of my 502.

I think if you consider some reasonable slip numbers, you will require about 5100 engine RPM to see 70-72 MPH with a 1.5:1 gear reduction in the outdrive spinning a 25 inch prop. I believe I figured my prop slip on my Rocket at about 13%. Does that sound about right?

It sounded like it was going to twist out of the stringers so thats probably right. I gps'd it and got 70.2 out of it. If it turned 5000 with the 25, there is no telling what it turned with the 23. The 23 wasnt labbed but it showed 5200 on the tack with the 23 @ WOT.