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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, four blade, 14 5/8" x 17"
Top Speed/Light: 41.9 mph @ 5,766 rpm
Top Speed/Heavy: 41.8 mph @ 5,820 rpm
0-to-20 mph/Light: 3.4 seconds
0-to-20 mph/Heavy: 4.3 seconds
Max economy: 6.09 mpg @ 3,250 rpm/22.0 mph
If three blades are good, will four be better? To find out we ran the Revolution 4, sort of a four-blade cousin to the Tempest Plus designed to deliver better hole-shot acceleration than the Tempest simply because it has more blade area. The Rev 4 is very popular on twin-rig outboard offshore boats because it really holds well in rough water, especially in following seas that can lift the transom and ventilate the prop. Merc also recommends the Rev 4 for stepped-hull boats, which send a lot of frothy, aerated water to the props. The extra blade should also produce more drag and thus lower top speed. That might be true on a faster or heavier boat, but in a more modestly powered rig like ours, the difference in performance between these two props is negligible. That said, the Rev 4 feels great from the helm. There’s pronounced bow lift at the last 5 percent of the trim range, it holds well in turns, and it offers better reverse thrust than the Tempest Plus. For general-use boating, overall smoothness is the key advantage of a four-blade prop.