SAVE AT THE PUMP WITH THE RIGHT PROPELLER, SET-UP
-- BBLADES Offers Tips for Maximizing Fuel Efficiency
With Memorial Day behind us come gas prices creeping up as the vacation and boating season begin, but one way to beat rising fuel costs is the right propeller and the right boat set-up according to the experts at BBLADES Professional Propellers.
With nearly 50 years of combined propeller know-how, the pros at BBLADES can help squeeze efficiency from a hull and drive combination that will help boaters achieve the maximum fuel efficiency for a particular set of performance goals.
Obviously, if flat-out top speed is what one desires, “fuel efficiency” becomes a relative term, but there are steps every boater can take to get more miles per gallon and use fewer gallons per hour. It is important to remember that while the following rules are generally universal, there are exceptions, and each boat and motor combination is different.
Slow it down
Lower engine rpm equates to less fuel use, that’s true. However, high engine rpm that is the result of an inefficient set-up, or the result of a high prop slip percentage (the difference between actual and theoretical travel created by one revolution of the prop), can often be corrected by changing to a propeller that has more blades, changing the depth of the prop in the
water or changing the pitch, diameter or other prop geometry. It is also important to establish the optimum cruising rpm for a given boat. This is done by testing the engine in 500 rpm increments and applying the efficiency formula. There are a number of devices available on the market to calculate prop slip and BBLADES can provide assistance in calculating both slip and efficiency.
From a dead stop, the natural inclination is to slam the throttle forward, then adjust the speed and trim as the boat comes on plane. However, the right propeller – usually a four or five blade – allows a boat to plane more quickly, and at a lower rpm, ultimately reducing fuel use. However, individual performance goals and boating styles must be considered. For example, on a V-hull with a sterndrive, a three-blade propeller will provide additional bow lift, and under speed help lift more hull out of the water, reducing drag and thereby increasing fuel efficiency.
Right tool for the right job
Stainless steel props provide a great deal of versatility. Because they are stronger, they maintain prop geometry better, which translates to better performance and longer life. Stainless is the optimum material for “blueprinting” or “lab-finishing” a propeller to achieve specific performance goals, but aluminum, nibral and even brass propellers for ski boats and big cruisers can be tweaked to improve performance and help reduce fuel use.
Again, set-up (how high or low the propeller sits in the water) and the number of prop blades can maximize boat and motor efficiency and the experts at BBLADES can provide guidelines on what might work best. In addition, BBLADES offers the marine industry’s best propeller test program, to help determine exactly how a specific choice will work on a specific boat.
And propeller manufacturers are constantly tweaking and adding new choices to their respective prop line-ups. For example, Mercury Marine has a pair of new three-blade props – the Inertia and the Fury -- with new blade geometry designs specifically for runabouts and bow riders. The company also offers venerable four-blade props like the Bravo 1 and Revolution 4.
Other manufacturers also offer four-blade wheels, such as Turbo’s Fusion 4 or the new Quad IV-X from Hydromotive.
For the high-performance boater running Mercury SSM VI or similar drives, there are a variety of choices among five and six blade options. Both Herring Propellers and Mercury offer a variety of models with prop diameters in quarter-inch increments. Mercury now offers different blade thickness on these screws based on engine horsepower, allowing for the thinnest, safest blade thickness in ranges up to 550, 800 and 1200 horsepower. Herring propellers will provide custom blade thickness based on the user’s need, a service which has made them a favorite among boat racers worldwide.
Both companies offer these propellers with rake angles of 15, 18 and 21-degrees, while Herring now offers 22 and 24 degree rake as well. With these so-called “surfacing propellers,’ the degree of rake will determine how much water the blades “bite” with each revolution of the prop. A higher rake will generally mean more thrust, as well as provide additional bow lift, reducing drag and increasing boat speed.
The best way to determine the right prop is to consult with the pros at BBLADES and take advantage of their test program. Both can be done on-line at
www.bblades.com or by calling 920-295-4435.
BBLADES Professional Propellers is a full service propeller company offering consultation, inspection and repair of any aluminum or stainless steel propellers; “Lab-Finishing” or “Blueprinting” of stainless steel propellers; competitive pricing on new props from Mercury, Hering, Hydromotive and Turbo; and the most comprehensive propeller testing program in the marine industry.
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