AT,
IMHO, only you can decide what prop works best on your boat.
What may work for one guy might not work for you.
There are too many variables at work here and the only way to sort them out is trial and error. Someone with a craft similar to your's and using it in the same manner (fish or ski, maybe just cruise) can get you close but until you actually run the boat, you won't know for sure.
Old school was to prop the motor to allow operation in the motor's max operational range (say 5200-5500 rpm) at WOT. This is a good starting goal.
From there you can look to achieve the best cruising rpm in relation to fuel consumption (a really big deal today) :cry:
I personally would take the 17, because it's new and start from there.
A lot of "propheads" on this Board. I'm sure they'll weigh in.
Good luck.