i have a 22' Bennington tritoon (2000 2275 lx) with a 2007 etec 150 ho. I currently have a 15.5x15p prop (aluminum). Under light load it is only pulling 5200 rpm. At wot it should be closer to 5800-5900. Questions I have are should I drop diameter and pitch to a 14x13p or just drop to a 15x13p? Thank you for any help.