I have a 2004 15’ Whaler sport with 60merc 2 stroke. Boat came with a 10 3/8 x 13pitch prop. Boat can easily exceed 6000rpm which is not recommended. Trying to find out what prop boat came with or what people are using . I can can tell you at 5000 rpm I’m hitting 25 mph and 29 at 5700rpm with two adults weighting in at 450 lbs combined and some gear. I see new super sports with 4s are running 13 x 14 pitch ss vengance and running 36.5 mph on the whaler site.