Repowering a 2001 Fisherman with t top with a new 3.3 L Yamaha 250. Looking for thoughts on prop. Having looked at the Grady website, i'm thinking a SWSII 17 inch would be great. But I'm also wondering what the same prop in 18 inch would do?? Old motor was a 2001 OX250 that turned 5300 rpm...