The SS over the alum, if stock alum, not enhanced design alum like the Turning Point Hustler, you have several things going:
Thin blades cut the water easier reducing drag and improving efficiency...like cutting water with a knife and a baseball bat....for an exaggerated comparison.
Cupped blades...tail end of prop is curved toward the water flow to improve thrust, especially in high transom mounts, high trim angles, rough water, tight turn, turbulent water conditions. Rule of thumb is it amounts to 1" of increased pitch.
High Rake...bending of the blades toward the rear sort of makes a water tube which increases thrust angle definition and when used with boat hulls that respond to such (Bass Boats with a "pad" to name one) due to hull design and adequate hp, causes bow lift which lifts the hull out of the water, reducing drag, and increases rpm and mph.
Then there is the progressive pitch whereby different parts of the blade are at a different pitch angles which is designed to improve performance over the full range of slow to high speed.
Then we have the ports. Holes in the barrel of the prop, just below the leading edge of the blade root allow exhaust gasses to expel during the hole shot (getting the boat from a stand-still to up on plane). This exhaust reduces the density of the water that the thrust of the blades is trying to push back to propel the boat forward......reduced resistance means that the engine is under less load. With a full throttle and less load the engine revs faster. Thrust is produced by a spinning prop with a certain torque. HP is (Torque x RPM)/5252. If you can get your rpms up faster, you develop your HP faster which gets you up on plane faster. The benefit of this is that you essentially have 2 props in one....a low pitched prop for hole shot and a high pitch to get that 65 mph "on the pad".
