Article by Capt. Steve Katz
Fuel Sense
With today’s higher fuel prices many boaters are paying more attention to their fuel usage. Some boaters are reducing the frequency of their fishing trips, some are shortening their trips, some are running at slower speeds along with implementing other fuel savings ideas.
Proven ways to reduce your fuel consumption
One way of optimizing your fuel usage is to operate your boat at the most efficient speed. That speed is where you travel the farthest with the least amount of fuel. If you own a later model boat, the manufacturer may have test reports matching your boat and engine combination. Using precision test equipment, they operate the boat at various speeds and record the fuel usage. Generally plotting the results on a graph. This allows you to visualize the optimum speed or RPM range that results in the best miles per gallon (or gallons per mile for some larger boats). Unlike a car, slower is not always more efficient, the power needed to push the boat through the water is not linear, most boats can achieve an optimum mile per gallon and speeds much faster than expected.
For example, a 31 Regulator center console with twin Yamaha 425’s gets the best cruising fuel mileage at 34 MPH. Instinctively, operating a slower speed, such as 24 MPH would reduce your fuel economy by over 10%.
Looking at another boat, a 70 Viking (2010 model) evaluated by Power and Motor Yacht in December 2010 showed that the 70 Viking obtained the best fuel mileage at 13 knots, which is understandable for a large boat like this, where slower is better for fuel economy. Though it may be surprising to some that the difference in MPG between 30mph and 37mph is only negligible .03MPG, again shows that there is a sweet spot for speed and fuel economy on every boat.
Fuel saving maintained tips
In your vehicle, spinning wheels does not get you far quickly. A boat's propeller is like a car tire, it transfers the engine's power to the water. A propeller that is not in perfect condition will not propel the boat through the water effectively, small nicks, bends, dings etc. can all add up to an inefficient propeller increasing your fuel consumption. Additionally using the correct propeller for your boat will help you get the best performance and often the best fuel mileage too. Finding the best propeller often starts with the boat manufacturer recommendations or propeller manufacturer recommendations along with on water testing. When testing different propellers be sure to carefully record, speed, RPM, and fuel consumption, this will help determine both the optimum propeller and the most fuel-efficient cruising speed.
Hull running surface or boat bottom
The bottom of a boat does not get much attention, it's hard to see and not overly exciting – but it is one of the most critical areas when it comes to performance. Regarding fuel efficiency, a smooth, clean bottom will move through the water with less resistance and therefore less fuel for the same speed. If your boat is kept on a trailer or stored out of the water, you may not have bottom paint and therefore maintaining a clean and smooth bottom is accomplished by cleaning and waxing. There are products such as Hull Maxx and Hullspeed, both modern coatings designed to be used on fiberglass hulls that promote an increase in speed and fuel economy after coating the boat bottom with their product. If your boat has traditional anti-fouling bottom paint, there are many options available that may increase your performance. One of the simplest tasks is to remove all the old bottom paint and start with new. Many boat owners choose to “soda blast” the bottom in place of manual hand sanding to strip the old bottom paint. Once the hull is clean, a new bottom paint can be applied. There are some “hard” bottom paints like VC Offshore, which is a multi-season, super slippery, hard vinyl antifouling paint that can help improve the speed and performance of your boat as compared to traditional ablative bottom paints or traditional single season hard bottom paints. VC offshore paint can also be burnished with fine bronze wool until a shiny, super smooth finish is obtained.
Trim
Most boats have a method of adjusting the running angle of the boat, using trim controls on the boat or engine, depending on the type of boat. The boat's trim also controls the amount of drag on the boat. A boat trimmed with too much bow up is dragging at the stern, while a boat with its bow down is plowing through the water and may be difficult to steer. Captains should use the engine’s power trim and trim tabs, if fitted, to achieve the best trim for the sea conditions and load on the boat. If your boat has a fuel flow instrument or MPG display, be sure to monitor the gauges while you operate the trim, often you will find the most comfortable ride will also be fuel efficient.
Improving your boat's fuel effecting is a combination of items that most boat owners can easily accomplish. Attention to these details will result in savings at the pump.§
