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Choosing the Right Prop
From its Oshkosh, Wisconsin, testing facility Merc offered us the use of a 1,900-pound Key West 2020 center-console rigged with a Mercury 150 FourStroke outboard, and a full complement of data acquisition gear. We tested each prop “light” (just the tech on board) and “heavy” (with 350 additional pounds in the boat), always with the 60-gallon fuel tank full.
Stainless steel, three blade, 14 5/8" x 17"
Top Speed/Light: 46.4 mph @ 5,791 rpm
Top Speed/Heavy: 43.9 mph @ 5,656 rpm
0-to-20 mph/Light: 3.6 seconds
0-to-20 mph/Heavy: 4.5 seconds
Max economy: 6.12 mpg @ 3,248 rpm/23.4 mph
The reason the Enertia propeller is offered in 1-inch pitch increments is because it was designed specifically for Mercury Verado outboards. The 5,800 to 6,200 peak rpm range of Verado outboards both is higher and occurs in a narrower band than two-stroke outboards, such as the Mercury Optimax, which has a peak operating range of between 5,000 and 5,750 rpm. Since prop pitch is essentially the final drive gear ratio for an outboard, smaller pitch increments allow adjusting top rpm to suit load conditions for engines with narrower top rpm bands.
The 17-inch-pitch Enertia propeller proved just right for our test boat. First, it allowed the engine to “turn up” to its maximum rated rpm. (That the engine slightly exceeded the recommended rpm range while lightly loaded with this prop is acceptable and, in fact, what we look for when testing boats. In “normal” use, most boats are loaded heavier, have the bottom painted, carry more crew, etc., all of which brings rpm down.) It also matched the top speed of the 18-pitch prop and the hole-shot acceleration of the 16-inch prop.