I have a Seafarer 228G with a 200hp Yamaha HPDI. When I got the boat, it had a 19" pitch prop, and would only turn 4700 RPM at WOT with full fuel tank and two people on board. I'm kind of a big ole boy, so maybe you should count it as three people on board. Anyway, I put a 17" pitch prop on there, and now it turns 5200 RPM at WOT. The hole shot seems better, and as best I can tell, the fuel burn is better. I don't have exact numbers, but I know I'm not having to put as much fuel back in on each top-off. It also helps to keep my foot out of the throttle, and not haul a$$ everywhere I go. I will admit that the Bubba in me comes to the surface on occasion, and I push the pedal to the metal sometimes. I think that for my motor, the preferred range of RPM at WOT is between 5500 and 6000. It may be that I need to look at a 15" pitch prop.
I hope this helps. Do some searches on this board and some of the other discussion boards, and you will find a lot of information. This board is excellent. There are some really good folks on here who are willing to share their knowledge and experience.
SwampGrizz