I have the older "white" drive, the aluminum propsets are B series, the stainless are C series. My engine is a carbed 275hp 5.7.
I have B5's on mine, they would be like an F5 or F6 in your drive series. I get 48mph in good water at 46-4800 rpm. I had B7's on it and the top speed was 50+ but it took a while to get past the 48mph mark and was not quite as spunky out of the hole. This is by speedo, but I have checked side by side with a couple of friend's boats and it is accurate enough for this kind of test. I did not try a B6 set, I had the B7's and B5's already in hand. I went with the B5's because the lake we frequent is small and no place to cruise, it only takes 10 minutes or so to go from one end to the other. We almost always have a load of kids and adults tubing and kneeboarding and skiing, that is our main use. It comes out of the hole fast with any load and planes very quickly. Cruises at 40mph at 3800-4000 rpm, 35mph at about 3500. It can hit 46+ with any load, and the engine has never gone past 4800rpm but I think mine has an rpm limiter as I have seen it in the manual.
If your boating is mixed cruising and watersports then the F5 or F6 would be a good choice. With lighter loads an F6 would work well, heavier loads then I would go with the F5. That F4 set is definitely too low of a pitch for your combo but is ok for now. An F5 should get you past 30 in the cruising and 45 or more top speed at the same rpm's. My boat is just a cuddy cabin, your boat does look heavier so I am thinking that an F6 might end up being too much pitch for when the boat is loaded.
This is mine in action, I putted thru the turn then gave it 1/4 throttle as soon as it was straight then hit full throttle about 7.5 seconds into the video...:
http://forums.iboats.com/showpost.php?p=1830246&postcount=1
