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Marine Advisory Program offers boaters tips to conserve fuel, save money

Submitted by Doug Schneider
Phone: 907-474-7449

06/23/08

HOMER, Alaska--Whether you are a commercial or sport fisherman, recreational boater, charter skipper, water taxi or tour operator, saving money on your vessel fuel bill can be as easy as slowing down.

It can also be as complicated as deciding whether to replace that tired old fuel-guzzling engine, or even the entire vessel.

"How much a boater saves on fuel is determined by many factors," said Terry Johnson, a Marine Advisory Program agent and boat owner based in Homer. He also has written articles on fishing vessel maintenance for a popular trade magazine.

"While there are some general steps all boaters can take, maximizing fuel savings comes down to a number of personal decisions about a specific vessel. No two vessels will be exactly alike."

To help boaters weigh their options, Johnson recently prepared a list of steps that can help lessen the impact of high fuel costs.

First on his list is simply slow down. Seems obvious, but the savings can be dramatic. For vessels that plow through the water--that is, they displace water rather than skim over the top--even a small decrease in boat speed will save fuel on most boats. Johnson said published data indicate that reducing power as little as 10 percent from full throttle will lessen fuel consumption by 20 percent. Back off the throttle to the point where the stern wave starts to flatten out and the savings will be greater. Reducing speed by just one or two knots can cut fuel consumption by 30 percent to 50 percent.

Running your diesel engine at its most efficient rating also will save fuel. Johnson said diesel engines are most efficient at 80 percent of maximum continuous rating, or MCR. That means they produce the most power for the fuel consumed. But be careful, most fishing vessels are over-powered and achieve their most efficient vessel speed at a power setting well below optimum engine speed and load. To get the most nautical miles per gallon you'll probably have to run your engine at a speed slower than its most efficient setting. Running too slow for too long, however, could damage your engine.

Things get a bit more complicated for vessels that plane or displace little water. These boats rely on skimming the surface; slowing too much causes the vessel to ride lower in the water, lowering fuel efficiency. Johnson suggests using a fuel flow meter, or keeping accurate records of gallons burned divided by miles traveled at different revolutions-per-minute (rpm) until you find your vessel's most efficient engine and boat speed.

Other tips for beating the fuel crunch:

Exhaust
Exhaust from a well-maintained diesel engine is virtually invisible. Black exhaust means the engine is overloaded, starved for combustion air, or has worn injectors. If the exhaust is white, there is an injector or valve timing problem, burnt valves, or bad gaskets allowing coolant into the cylinders. Blue exhaust indicates oil in the combustion chambers from worn rings or valve guides, or a turbo seal failure. All of these problems decrease engine efficiency and increase fuel consumption.

Prop
When the boat is out of the water, check the prop for bent blades, dings, or eroded edges that cause fuel-robbing cavitation. While underway, check the propwash for excess turbulence and bubbles that suggest a prop that's too small or has too little pitch. And check your exhaust stack for black smoke that would suggest overloading. Use your tachometer and pyrometer to ensure you have the right prop. This can change as the use of the boat changes or it gains weight or resistance from additional equipment or modifications. The engine should quickly reach rated rpm and exhaust temperature should be within manufacturer's specs; if not, the prop is too big or has too much pitch. If the engine exceeds rated speed or exhaust temperature is too low, you may not be wasting fuel but you could be causing long-term harm to the engine due to carbon buildup and cylinder glazing. Use a computer prop sizing service to ensure you have the right diameter, pitch, blade area, and prop configuration.

Hull
Marine growth on the bottom of a boat saps power and wastes fuel. Get the weeds and barnacles off and keep them off with proper antifouling paint. The smoother the paint, the less friction, so find the right paint for your hull. Sponsons, struts, sea chests, keel coolers, transducers, and stabilizers all increase hull drag. You probably need those more than an extra fraction of a mile per gallon, but if there's something below the waterline you don't need, get rid of it.

Electrical system
Do you need to run a diesel genset around the clock or can you use batteries and an inverter for your "hotel" power? A larger alternator on an underloaded main engine may produce electricity more efficiently than a standalone generator. Can you cook on an oil or propane range rather than an electric one? Consider adding a wind charger or solar panels to reduce the fuel cost of electricity.

Steering
You burn fuel to push your boat through the water, but if it's not going the shortest distance to your destination you may be wasting fuel. If there's play in your steering, adjust it to eliminate as much as possible. A good autopilot can steer straighter than any helmsman. Even if you have a great autopilot, watch your wake and you may see that you're zigzagging through the water. The pilot's control head probably has adjustments that change steering parameters and allow you to minimize delayed or oversteering in calm conditions. Modern units even have a no-drift mode that compensates for wind and current.

Plan your trip
Remember when vessels used to depart on the tide? It was not so necessary with big engines and cheap fuel, but now routing to take advantage of tides, currents, and predicted winds can save money. Remember, the shortest distance between two points on the water is not necessarily a straight line. Tide and current tables, and oceanographic current charts, can indicate ways to get a boost from nature. Good weather forecasts help you avoid headwinds or delaying sea conditions, and also suggest chances to get a boost from tailwinds.

Vessel weight
More important on a planing or semi-displacement vessel, weight control reduces the amount of power needed to achieve a given speed. Boats quickly fill up with supplies, gear, and spare parts. On short trips, it may not be necessary to run with full fuel and water tanks. Use trim tabs or shift passengers, gear, and ballast to achieve proper vessel trim. On displacement boats, additional weight may improve seakeeping and in some cases may actually improve fuel efficiency by helping the boat proceed more directly through the water.

Keep good records
You only know whether you're making an improvement (or making things worse) if you have good numbers on vessel performance, both before and after changes. At every fuel-up you should record fuel replaced, operating hours (from your hour meter or engine hour logbook), and if possible, distance traveled. Other observations such as changes in coolant and exhaust temperatures, oil temperatures and pressures, and speed over the ground (as indicated by GPS or LORAN readings) should be logged.

Do the math
Fuel is only one of the costs of your operation. Capital expenditure (the price of new equipment), and the value of your time and that of your crew, are also costs. The cost of a solution, such as buying a new engine or even a new vessel, may be greater than the savings that could be realized. As fish prices, fuel costs, regulations, and other factors change, it is important to recalculate the trade-offs.

For more information, visit the Marine Advisory Program's Alaska Boating Fuel Efficiency Resources Web site.