Prop Help
 

I have a 2015, 2104 frontier with a 2015 175hp Suzuki 4 stroke. My prop is a Suzuki 3x16x21.5 R. With 2 people, fishing gear, small ice chest, 3/4 tank fuel and whatever else someone usually has when fishing I can turn around 5100-5300 RPMs and top out around 47-48 mph. The guy I bought the boat said he would turn around the same RPMs but for would do 56-57 mph.
My question is, why isn?t the boat performing like that anymore? And if you have the same boat what size prop are you running?
What are my options? Thanks in advance.

The operating range is 5500-6100 rpm's. I personally think you should be turning a 19 pitch prop. which should be a gain of rougly 500rpm maybe even an 18 pitch. but either way I can't see you gain 8-10mph. Also was he checking mph on gps or speedometer installed gauge?

I love you, the check is in the mail, my boat goes 65 miles an hour.:)