Well, in that Avatar of mine that's my 90 on a 17' alum boat at 50 running a 24p Ballistic and 5600 rpm with just me. But the boat and the load really are what determine the pitch. Since the first set of numbers were right on, why not expect the next set to be right on also. First of all you need to know the brand and model of your prop. You might get on here and look at their props to get an idea as to what looks like yours...kind of iffy, but better than nothing if you have no number cast into the hub.
Since we are working with +/- 15% lets swag a 1.15 x 17P for 19.55. 19 is a common pitch as it is odd as your 17 is odd and general run of the mill props a lot of times jump pitch 2" in their prop line up.
That certainly won't over do it and if it's still a little shy and your prop can be cupped by a quality prop shop, you can cup it, or if already cupped, increase it if the ship is learned and thinks your specific prop can take what they want to put on it. Believe it or not, from what I have read, different props have a max cupping angle before predictable things are no longer predictable.
By the way, when you have settled on a number, go back to the top of the page and get back into Boat parts and accessories and order it from here. Good prices, courteous people, guaranteed satisfaction.....if you don't run it on props, and it helps to pay the rent and keep this forum alive.
Good luck.
Mark
