I have a 1973 Stevens flat bottom with a BBC 454. The engine has 400 to 425 HP. It has a 12 degree Casale box with 12% gear. I have 2 props, 1 is a 3 blade 12 X 16 (brass) and a 2 blade 13 X 15 (steel). The boat is mostly used for weekend cruising but id like to pick up some top end speed. Would it be worth while going to a 18% gear and which prop would be best for my application. Thanks for any help.