Well, I’m thinking that the pulling to port and correct pitch for your rig are two separate issues. Try trimming the engine out or in a bit to minimize the pull. How about engine height? Is the Anti ventilation plate about even with the bottom of the boat?
As for the correct pitch, kind of hard to say without any tach readings from any of the props. The boat is flat bottom, so planning shouldn’t be tough. But, I’m gonna stick my neck out and "guess" that the 11" pitch might be too much for heavier loads or if you are pulling the kids on tubes/skis. Who knows though, try it out with the heavier loads that you mention to see how it accelerates and how the engine sounds at WOT. I’m assuming you don’t have access to a shop tachometer.
You had a 9" pitch prop before, I am assuming that one accelerated great but might have been over revving a bit at WOT….What made you think of changing pitch sizes? Again, I’m "guessing" the 10" pitch prop is probably the best "all around" prop for your rig.
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