Props, Tops and Trim
We get tons of mail about which propellers are best for a particular boat. Unlocking the secrets of fuel efficiency on our Bluewater 2550 can give you insight for correctly propping your own boat. “Props are important to efficiency,” deadpanned Mike Rogge, senior engineering technician for Evinrude and our prop specialist for this test. His no-nonsense delivery and demeanor confirmed our instinct to test the effects of props on fuel burn with him.
It’s important to note that the primary criterion for selecting a propeller is to make sure it allows the engine to “turn up” to a speed within the band designated by the manufacturer — usually within 500 revolutions of absolute top rpm. This ensures a long life for the engine, neither lugging it down nor letting it over-rev. But within that band, you can select a variety of props that will allow the engine to turn up, yet have differences in pitch and number of blades, plus possess more subtle characteristics such as rake, skew and cup. Evinrude offers demo props through participating dealers for the purpose of allowing their customers to pick the best props for their needs.
Our Bluewater was run and turned up with eight different stainless-steel propellers. Not only did fuel consumption vary wildly, but also the thirstiest set of wheels allowed the engines to rev up only to the low end of the range specified by the manufacturer. The most fuel-saving wheels allowed the motors to rev to near the maximum of that range, however, meaning they’ll not only save dinero at the pump, but will also pay dividends in increased long-term durability and reliability.
So, the right prop matters, meaning it’s worthwhile to beg, borrow or steal a selection to try out on your boat. What else can help improve your boat’s efficiency?