I had a 8hp Johnson longshaft that planed off a 16ft BassTracker, eventually. It Gps'd at 14mph. I have a 1985 Evinrude 15hp now, that always gives me 26mph on a 12ft rowboat. The 25hp pictured here always gives at least 29mph on 14ft boats. All these motors were found on a budget using patience.
My inclination is to stay away from 4stroke motors because of their weight. Another factor is their powerband. It is not as well suited to planing a boat. They don't make the power down low that the 2strokes do. Servicing 4stroke carburetors is a nightmare from what I am hearing from several dealer friends. In a perfect world, where nobody ever leaves gas to sour in the carb, this is not a problem. Here on Earth, we forget, or our gas is contaminated, or whatever. On a good ol' two stroke, you buy a readily available kit, clean a few parts and off you go, cheap and easy. In addition 4strokes require periodic oil and filter changes, valve adjustments, and cam drive adjustments. 2strokes always have fresh clean oil and never need valve train service.
For my time and money, looking around for a nice freshwater, low hours, 2stroke engine, 15-25hp, is a way better investment than a new four stroke. You'll thank yourself the first time you have to carry it down to the water. Plus you'll have a couple a grand in your other hand to help balance it out. End of year storage is as simple as run'er-outa-gas and fog'er-'till-she-quits.
Again, this is all just my 2c worth.