What is the best RPM for a 1992 150hp 60deg eagle series engine. My boat would only turn around 5300, but after installing a 7" setback plate it now turns 6100-6200. It is on a 274FS Stratos 18' with a 23" Shooter @ 64mph GPS. Should i go with a 24 or 26 Raker to bring it down some?