Better practices can save fishermen fuel expenses

TERRY JOHNSON

July 03, 2008 at 11:56AM AKST

Increased fuel prices are hurting commercial fishermen and charter boat operators.

Saving fuel is a complex and personal issue, dependent largely on your particular vessel and how you operate.

Here are tips to consider for lowering your vessel fuel costs.

• Slow down.
In a displacement vessel, even a small decrease in boat speed saves fuel. Data show that reducing power by as little as 10 percent from full throttle will save 20 percent in fuel.
The biggest power drain comes in making the bow and stern wave that every displacement boat drags along. If you back off the throttle to the point where those waves start to flatten out, the savings will be greater. Cutting speed by one to two knots can cut consumption by 30 percent to 50 percent.
Diesel engines are most efficient at 80 percent of maximum continuous rating. That means they produce the most power for the fuel consumed. Most fishing vessels are overpowered; they achieve 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. Too slow for too long, however, could damage your engine.
If yours is a planing or semi-displacement hull, the matter is more complicated. Slowing too much can decrease fuel efficiency. Use a fuel flow meter or keep accurate records of gallons burned divided by miles traveled at different revolutions per minute until you find the most efficient engine and boat speed for your vessel.

• Examine your exhaust.
Exhaust from a well-maintained diesel engine is virtually invisible.
Black exhaust indicates the engine is either overloaded, starved for combustion air or has worn injectors.
White exhaust is symptomatic of an injector or valve timing problem, burnt valves or bad gaskets allowing coolant into the cylinders.
Blue exhaust signals there is oil in the combustion chambers from worn rings or valve guides or a turbo seal failure. All of these problems decrease engine efficiency.

• Check your prop.
When the boat is out of the water, check the prop for bent blades, dings or eroded edges that indicate cavitation. These are fuel robbers and should be repaired.
While under way, check the propwash for excess turbulence and bubbles that suggest a prop that’s too small or has too little pitch.
Use your tachometer and pyrometer to ensure you have the right prop. This can change as the use of the boat changes or gains in weight or resistance from additional equipment or modifications.
The engine should quickly reach rated rotations per minute, and exhaust temperature should be within manufacturer’s specs. If that’s not the case, 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 carboning and cylinder glazing.
Use a computer prop sizing service to ensure you have right diameter, pitch, blade area and prop configuration.

• Maintain the bottom.
Marine growth on the bottom 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 skin friction there will be. 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.

• Rethink your 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.

• Check your steering.
You burn fuel to push your boat through the water, but if it’s not going the shortest distance to your destination you’re 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 route and timing.
Remember when vessels used to depart “on the tide?” It wasn’t as necessary with big engines and cheap fuel. But now, with higher fuel prices, 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 opportunities to get a boost from tailwinds.

• Reduce 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 with supplies, gear and spare parts. On short trips or openings 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, however, additional weight may improve seakeeping and in some cases may actually improve fuel efficiency by helping the boat proceed more directly through the water. Each case is different.

• 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 your crew’s time are also costs. The cost of a solution 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 tradeoffs.

Terry Johnson is an agent with the Alaska Sea Grant Marine Advisory Program. He can be reached at (907) 235-5643 or terry.johnson@uaf.edu.