Prop for Formula
 

I have a 1993 Formula 271. I have owned a couple other go fast boats but the boats had the correct props when I purchased them. This boat has a 502 mpi with a pro charger. It also has an imco. The gear ratio in drive is 1.50. Boat runs excellent, it is slow out of the hole getting on plane. Currently it has a 4 blade 28 prop. It is only hitting 4000 rpms at 60 mph on gps. I am looking for more speed but still useable to cruise. With the current set up cruise speed is roughly 38-40. Any help would be greatly appreciated!

You need drop down to about a 24" Bravo 1. You are really lugging that engine with a 28" and risking detonation. Let cruise speed and cruise rpms fall where they may. You need to be propped for correct WOT rpm which is 4600-5000 rpms. The closer to 5000rpms, the better. Dropping 4" in pitch should equal about 800 rpms.

Thanks
 

Thanks griff. I know it is definitely not where it should be. This boat is awesome and the previous owner did a lot of work, but when it got down to testing and tuning they did very little. Example; the prop. A buddy has a 26 that i can use just for testing this coming weekend, I am going to see how it does, but I think the 24 may be the better choice.