What is the best prop for the Yamaha SHO 250? We have a 2009 Puma FTD with Merc Pro XS 250 & 26 Fury but we also have a Xpress 21ft with 250 SHO Yamaha. Boat came from factory with four blade stainless and with jackplate at 1/2 up and trimmed up we can only turn 4400 rpms. Do we need VMAX series three blade prop? 26 or 27? Vents or ventless? Any help appreciated!