[Destroyer]

What do you want the boat to do? Less pitch = more power for pulling and the like, more pitch = more speed but less power. You went from a 19 to a 17, and now you want to go to a 15, but 3/4 of an inch wider dia. than the original 19. First off can you swing that dia without hitting anything? If so I would do like countless others have advised in the past on this site.. try before you buy. There is nothing worse than having a brand new $450 prop sitting in your garage because you don't like the preformance. Most marinas that sell props will have test props you can use to find what you are looking for. Stainless or aluminum, as long as you are hitting your engines WOT rpms you are in the sweet spot. Too low rpms, downpitch, to high rpms, uppitch. There are too many variables for anyone here to be able to make anythig other than a general call on what prop or pitch you need. The weight of your boat, the number of people, how much gear, is it bottom painted, what kind of water (smooth or choppy) and a ton of other things I've forgotten... all can effect your selection.