My marina also has a 17" pitch on my 115Hp 240DF. First time out got only 28 mph 2 people but understand for 26 footer that's about right. However had a lot of cavitation problems which has resulted in a lot of changes. I see Yamaha has a lot of pontoon performance propeller that are recommended when you use their site that Boomer mentioned. However when I called, and talked to a tech he claimed the 17" that it came with was right. Very confusing site states one thing and actual tech say something else. Let me know what you decide and if you try something that's better please let me know. If one of the Pontoon Performance work in the long run the cost of $400 will be cheap.