I will say... I had my 2-stroke days with the most HP I could hang on the back of the smallest, fastest boat I could find. That fun but these days I'm happy with my 4-stroke F115 on a 19' boat rated for 150 Max HP. I cruise at 4200-4400 RPM (in the sweet spot around 24-25 MPH) and enjoy almost 5 MPG. At WOT it will do about 38-39 MPH at 5900-6000 RPM depending on load but,let's be serious, how often can you find water that you really want to be running 40MPH+ unless you boat on a distant inland lake or early on a sunday morning?
Furthermore, I don't care that my Yamaha Tech claims a 4-stroke can run all day at 5000-5500 and "loves it". I can HEAR how hard that engine is running when all those valves in the OHC are screaming. Outboard engines are expensive and they are under great stress ALL THE TIME when running. Unlike a 4-CYL car rolling down the highway at 60MPH turning 3,000 RPM and getting 30 MPG, at WOT I'll get maybe 3.5 MPG and see 38 MPH. Running a boat is like driving a car up Mount Everest ALL THE TIME as far as the engine is concerned. Lift you foot from the gas peddal in your car and you can coast another 3 miles... pull the throttle back on your boat and you come to a STOP. Long story short... BABY YOUR OUTBOARD IF YOU WANT TO SEE THE SAME HOURS THE COMMERCIAL FISHERMAN GET OUT OF THEIRS! 4-strokes will last for 1000's of hours if you don't abuse them the way you did the old 2-strokes that could handle those high RPM's all day long.