Whenever gasoline is spilled in the bilge, anything more than a few drips, the response should always be to call the fire department. Don't take a chance. A quarter cup of gas in the bilge can blow up your boat and anyone in it! That will really spoil your day.
Flame arrestors are required on marine engine installations. Clean them with soap and water. Drip pans must be fitted under the carburetor for inboard gas engines.
Keep fire extinguishers near engines, stoves, and sleeping areas. Keep one in the cockpit! An electronic bilge sniffer designed to detect gas or propane can save your life. Quality battery-operated detectors are capable of detecting carbon-monoxide, a deadly and odourless gas from stoves, heaters, engine exhaust and generators.
Always put gas containers on the ground before filling. Never fill a gas container inside a boat or a vehicle. Keep the nozzle in contact with the can to prevent sparks. Use only containers designed for gasoline (they will be red and labeled by a standards association such as UL or CSE). Never fuel near any kind of flame or cigarette!
Fires are common at filling stations when filling metal gas cans placed on plastic surfaces (like truck liners). When gas flows into a metal can it causes a static charge to build up, which cannot dissipate if the can is sitting on a plastic surface. Then if the gas nozzle is not in close contact with the gas can, a spark can occur between the gas can and the fuel nozzle. At the neck of the gas can, gas vapour can ignite, causing a fire.
E15 gasoline — fuel blended with 15 percent ethanol — voids many engine warranties. Ethanol in gasoline can cause phase-separation. When moisture is introduced to an on-board fuel tank because of variations in temperature or high humidity, it binds with the ethanol and settles as sludge in the bottom of the tank. Ethanol has also been known to be corrosive to metal fuel tanks and engine components. Check your engine manual before using it. pure-gas.org lists every station and marina in the U.S. and Canada that sells ethanol-free gas.
Boats are now using soydiesel, an environmentally-friendly, oxygenated fuel made from soybean oil (diesel is made from petroleum). It has lower emissions of just about everything except nitrogen oxide (bad), but there isn't any smell, it's biodegradable if spilled, and you don't get that black stuff on your stern. Of course, since it's only made in Kansas and Massachusetts, the price is almost double the regular diesel. Too bad.
Marinas charge more for fuel for many reasons. Low volume means no bulk discounts. Dockside installation costs are higher. Dock staff is needed to help boats tie up and safely fill the tanks. Insurance costs are higher due to environmental fines for leaks or water contamination. (Note: Filling gas tanks with gerry cans is banned in many marinas because of insurance liability for spills and fire.) Learn a few tips "How to Save Fuel" - I'm sure you'll find something useful.