I've got a '76 18SF with an '09 DF140 Frankenmotor ('04 115 mid and bottom and '09 140 top and PTT with a fresh power-head (new in 2010). Swinging a 3 blade 14/20 prop it takes a little while to get out of the hole and you get a little bit of a sky shot so I don't think it's the perfect prop, but on my last ride of the season 3 weeks ago I hit 39.5 knots in a slight chop (just me on the boat and light fuel). I have not tracked fuel consumption because most of my fishing is short hops in the Long Island Sound. It does cruise fast at 4000-4500 rpm and seems to sip fuel (I have a new 50 gallon tank and the needle just doesn't move).
I have a raised transom and 25" shaft motor. I agree with everyone that it is stern heavy - I moved the batteries (run duals) far forward in the console and also moved the console forward about 5". I also have ping pong scuppers. But I plug the scuppers when I'm anchored up or drifting and pull the plugs when underway. Without the plugs it gets wet with two big guys fishing in the back (I run two 500 gph bilge pumps and also put corner drains in the deck).
Overall I think it is a great combination of speed and efficiency. If you went through the trouble of raising the floor it would be about perfect (but then I also hate to give up the freeboard)
