Re: Pressure wave
As far as the boat goes, we try to get the wetted surface to a minimum which means less drag. You can try to get the hull to "air out" in several manners. First, hull design. Boats that have a lot of natural lift vs. those that don't. Pad bottom hulls, tunnel hulls, modified V (slot bottom), deep V, shallow V, tri-hull, hulls with hook, hulls with a rocker etc.
Second, use props that compliment any given hull design. IE - boats that have a lot of natural bow lift don't need a bow lifting prop, those hulls will benifit more from an over-all lifting prop.
Then there is balance. Moving the load in the hull to specific places or changing the setback to move the fulcrum point.
As for the gearcase, we try to get as little as possible of it in the water. The most efficient scenario would be to hide the bullet of the case behind the boat almost like a surface drive unit (Arneson, Kama etc).
There is a "wave" or vortex in front of the gearcase. At speed the nose will push water away from case and the water will then naturally curve back to the side of the case. Just in front of where the water comes back to the case is air. The faster you go, the further back that pocket of air is. At some point, depending on gearcase design, the prop will get into that pocket of air. At that point the prop loses bite and the boat probably takes a hard 90* left hand turn. Sometimes the boat will snap roll. It ain't pretty. That's what's known as "blowout". A lot of folks refer to blowout as what happens when a prop starts to ventalate. Either getting on plane or in a turn but while they're similar in that the prop loses bite, they're really two completely different things.
