I have a 93 liberator 221 with a 502 omc with motor work done, its around 525 hp. at the crank, im useing the stock prop on it and gained a solid 2 mph the stock prop I have is 20 1/2 x 14. Ive tried a 23, and a 21, but seems the stock prop works the best. gps numbers are 64mph at 5100 rpm. just wondering if any one has tried any other props that works best for you.

sorry my prop is 14 1/2 x 20 not 20 1/2 x 14

My 95 Four Winns with OMC KC drive liked the the REV 4 & hydromotive QIV the best. Both performed better than the 3 blade M+ & slightly faster.

What kind of speed were you getting in stock form? It seems like you would be faster than 64 with an additional 100 hp.

I was getting 62 mph with the stock motor, I have a friend that has the same boat and motor that I have and his best on gps is 62 mph so i think the 2mph gain is close but I think it should 3 to 5 mph gain with a 100 hp gain. I think I need a prop thats going to get the hull out of the water better, the rougher water the faster the boat goes. I need another 100 to 300 rpm for max power.

hook in the hull???

I had an 88 Liberator that had a factory hook!

A hook? not sure what that is.

A "hook" was pretty common in the performance boats of that era. They were heavy and a "big" engine might turn out 400HP. If you lay a straight edge on the bottom of your hull, you will likely see that the bottom hooks down closer to the transom. The hook functioned much like a trim tab would to help a heavy and relatively underpowered boat get on plane. Depending on where the hook is, you might be able to remove it and gain some top end. I would discuss that with a good glass guy and someone who's done it before with your exact setup before making the investment.

Thanks! I have heard of that, I have friends that work at four winns and they have told me about it. looks like a lot of work to do.

Interesting thread, I picked up a 221 Lib today with an 502 and the guy told me it had the wrong prop (14.25 x 24) since the stock one was stolen, so I was looking and it lead me here. Sounds like the stock prop may be the best starting point anyhow. My boat is all stock with the exception of Stainless Marine Headers.