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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.
1. A modern aluminum prop works fine, but a stainless-steel prop will outperform aluminum in every way. Only you can decide if that overall performance is worth $600.
2. In our test situation, the four-blade prop matched the performance of the three-blade stainless-steel prop, and it felt better from the helm. I’d spend the extra $80 for the Revolution 4.
3. It’s better to be underpropped than overpropped. A boat running too much prop pitch will feel doggy all over the operating range because the motor is always working a little harder. On the day you have a full load of passengers it will feel like a real slug. If you never run your boat near full throttle, there’s nothing wrong with running one size underpropped and enjoying better acceleration, not just on hole shot but also in the midrange, which is where you really run the boat.
4. If your boat already planes in four seconds, there’s not much room for improvement. If your boat planes in six to eight seconds, a better prop might make a difference you can really feel.
Our testing for this story only serves as an example. The tricky element of propping is that there are many variables that can affect how a particular prop works on a particular boat, including boat weight, weight distribution, engine/drive height, the hull form, the way water flows to the prop, the power curve of the engine, and on and on. The Mercury website, for example, has a prop-selector tool (mercurymarine.com/propellers/prop-selector/#) that will get you in the ballpark, but from there you’ve really got to demo each prop to see how it feels on your boat. Find a dealer that will let you test-drive a number of props before you buy. You can do your own testing with a GPS and a stopwatch, but also pay attention to how the boat feels with each prop. That’s an element of performance you’ll appreciate every time you run your boat.