Need for Speed in the Outback

[jmondl]

So, this past weekend I was working on some barefooting behind my 2010 Outback DD 325 hp, and needed about 43+ mph. However, the Outback peaked at about 42 mph pulling me barefoot. When I later opened the boat up without pulling anyone, the boat topped out at 44 mph at about 4400 RPM. I know I can replace the prop, which I probably will, but I was surprised the engine refused to push past 4400 RPM. My last boat (V-6 190 hp) hit over 5000 RPM. Will a different prop increase the top RPM, or is there another trick, or is this just the normal RPM of the engine? If anyone has other insight into picking up a few more MPH without losing too much hole-shot, I welcome the advice.