Clean Boater Program

Engine, Battery Maintenance, Fueling

According to the EPA, as much as 30% of the fuel and oil contained in a standard two-stroke outboard engine may be discharged unburned into the air along with the exhaust. Some amount enters the water. Hydrocarbons and other fuel components cause environmental concerns. The batteries in your boat contain chemicals such as sulfuric acid and lead that can leach into the ground if improperly stored for the season.

Reducing Pollution from Engines

Thanks to the Clean Air Act of 1990 and a regulation passed by the EPA in 1996, marine engine manufacturers needed to reduce engine hydrocarbon (HC) and nitrogen oxide (NOx) emissions in outboard and PWC engines 75% by 2006. There are two types of outboard engines that greatly reduce the emissions and unburned fuel. The direct fuel injection (DFI) two-stroke, sprays the fuel into the combustion chamber after the exhaust port closes. The four-stroke utilizes valves to control the timing of fuel and exhaust flows. These technologies result in greatly improved fuel economy, smoother combustion, reduced noise, improved idle and lower emissions.


Petroleum-based fuel is no different from other hazardous materials. The most effective way to minimize its harmful effects on the environment is to reduce consumption and prevent spills. Fuel spills during refueling are common. Most fuel docks don’t have automatic shut-off valves to prevent topping off. When the fuel expands in the vessel’s tanks due to heating, overfilling can cause fuel to escape out the vents. Be careful! Fuel spills are harmful to marine life as well as to boats. Exposing hulls to fuel spills deteriorates the finish.

Ways to Reduce Your Consumption of Fuel
  • Keep the engine tuned. Proper ignition timing and clean spark plugs assure better mileage. Inspect the carburetor for proper float level, correct jetting, and smooth choke operation. Check the fuel and oil filters regularly. If your boat uses alcohol-based fuel, be aware that it may deteriorate fuel lines. Replace bad Balance your load. A balanced boat can plane quickly, reaching the desired speed with less plowing.
  • Slow down. A wide-open throttle can increase fuel consumption by 50% or more over mid-range speeds. As you "trim" the boat, maintain RPMs at the level recommended by the manufacturer.
  • Watch your weight. The lighter the boat and its load, the fewer horsepower are required to propel it, allowing greater fuel economy. Drain bilge and holding tanks properly before departure. Store unneeded supplies and equipment ashore.
  • Avoid excess idling. Whenever you have to stop, turn off the ignition. A warm engine restarts easily without choking.
  • Check your propeller. A damaged prop will waste fuel. Keep propeller blades clean; replace or repair props that have damaged blades. Adjust diameter and pitch for the level of activity you use most.
  • Check the tides. Boating against the tide is like running against the wind—it takes more effort. Plan your route to make the tides and the currents work to your advantage.
  • Keep your boat bottom clean. Growth on your hull causes underwater drag.
  • Purchase a low emission, fuel-efficient engine.
Disposal of Engine Batteries

Recycle your spent lead-acid batteries at the point of purchase to ensure proper disposal. Your marina may have a battery collection area.

Under Connecticut’s "core charge" law (CGS Section 22a-256h), anyone buying a new engine battery can return the old battery within 30 days, and get a refund of $5 for the "core charge" they paid when they bought the new battery. In addition, retailers are required to take up to three batteries from anyone NOT buying a battery (in such cases there is no core charge refund, however). For more information on the "core charge" law, call the Recycling & Source Reduction Division at 860-424-3366.

Other Batteries Onboard

About 50% of the mercury and 25% of the cadmium used in the U.S. goes into alkaline batteries that are not presently recyclable. When spent, those heavy metals find their way into landfills or incinerators where they can contaminate the air, soil and groundwater. Consider using rechargeable batteries with electric or solar rechargers for electronics onboard. The fewer batteries used, the fewer harmful metals go into the municipal and hazardous waste landfills.

Tips for Engine, Battery Maintenance and Fueling
  • Keep your engine well tuned to prevent fuel and oil leaks.
  • Check fuel lines for damage. Replace with alcohol resistant hoses.
  • Refuel at the end of the day, listen to the filler pipe to anticipate when the tank is full and leave room for expansion. If you overfill your tank, you can actually lose fuel out of the overflow vents during the heat of the day.
  • Fill up your tank to 90% capacity for winter storage to prevent deterioration of the stored fuel. This allows room for expansion of the fuel in spring when the outside temperature rises.
  • Consult your local boat dealer regarding whether or not any fuel additive (stabilizers or dry gas) should be used with your engine. Buy only what you need.
  • Use an absorbent pad or donut around the deck fill to catch backsplash and attach a temporary collection device to your hull to catch overflow from the tank vent. Pads can be airdried and reused.
  • Overfilling prevention devices are easy to install. They help you save money, reduce pollution, prevent fuel stains on the hull, and prevent refueling fires. Another inexpensive option is a fuel catch cup that maybe installed underneath the fuel overflow vent.
  • Ask your marina about a fuel/air separator. Installed in the vent line of the fuel tank, a fuel/air separator allows vapors to escape during refueling, keeping fuel where it belongs—in the tank.
  • There are many lightweight, compact solar panels designed for boats that can be used to recharge batteries, run appliances, and heat water.
  • Use rechargeable batteries for your Emergency Position Indicating Radio Beacons (EPIRB), flashlights, man-overboard lights, or other items onboard your boat. Check batteries for adequate capacities for use.
Content Last Updated on December 26, 2019.