Where's the power?

[able archer]

I have a 2011 Zodiac Pro 15 man Rib with a Yamaha 150 Four Stroke. Yamaha perfomance tested this exact boat, motor and prop.(the prop is a SS 13-3/4 x 19) Yamaha states in there test the boat reached a max rpm of 5800 and a speed of 52 mph. My boat on the other hand only reached 5100 rpm and 42 mph. The conditions were near identical with Yamaha's test: sea's, wind, weight etc..
My question is does anyone have a similar boat and motor setup as mine and what kind of performance are you getting out of it?

[captnjack]

You have a bunch of extra weight aboard? Agree you should be turning higher rpm and faster with a 150hp. Is the prop the EXACT same prop or maybe a slightly different model with different blade dimensions SS vs. Ali or something else changed?

[sburt10]

Is the engine at the same hight ?