Ethanol And Your Marine Engine (E-10)


Today’s gasoline which can contain up to 10% ethanol is commonly known as “E-10.” Some older model fiberglass fuel tanks in boats may not have been manufactured to be compatible with E-10. Fiberglass softening and tank leakage are possible. With any fuel system, if you suspect a leak, you should fix it immediately. Boats with older fiberglass tanks have suffered engine damage due to fiberglass resin compounds carried through the fuel filters into the engine and deposited on intake valves. If in doubt about your tank’s compatibility, contact the manufacturer. E-10 gasoline has been used in the Midwestern United States for over a decade. Experienced Midwest boaters and the BoatUS Foundation share these suggestions:

  • If your fuel system has a build-up of contaminants, E-10 may act as a solvent, remove the contaminants from your fuel tanks and fuel lines and carry them into the fuel filter. Keep spare filters on your vessel, so if a filter becomes clogged while at sea, it can be replaced. As contaminants are removed from your fuel system this problem should subside;
  • It is critical that water be prevented from mixing with E-10 to avoid phase separation. Once phase separation occurs, fuel stabilizers or water separators will not reverse it. At this point, the only remedy is to have the gas and ethanol/water professionally removed from the tank. Using the remaining gasoline is not recommended;
  • When storing your boat, add fuel stabilizer and fill your tanks to about 95% capacity to leave room for expansion. Phase separation typically occurs when boats are stored with tanks only 1/4 – 1/2 full;
  • The increased oxygen in E-10 “enleans” the air/fuel ratio leading to more complete combustion and reduced emissions. The air/fuel ratio may need to be adjusted on engines without automatic controls.


Links to more information on E-10 gasoline:“Fiberglass Tanks and Ethanol”

Print DOBOR’s E-10 Flier  

If you have used E-10 gasoline and have an opinion on this blended fuel, please send
your comments to the
Division of Boating and Ocean Recreation.



Non-blended fuel is currently being offered:

On the Big Island:

at the Honokohau Harbor Fuel Dock (Mauna Kea Petroleum)

at Gentry’s Kona Marina Honokohau Harbor, 74-425 Kealakehe Parkway, Kailua-Kona,
(808) 329-7896 TOLL FREE 1-888-458-7896

at Mountain View Gas n’ Go, Volcano Hwy. 11 Mountain View
(808) 968-6144

at Queen K Tesoro, 74-5035 Queen Ka`ahumanu Hwy, Kailua-Kona


On Maui:

at the Lahaina Fuel Dock (open from 10 a.m. to 3 p.m. Mon-Fri)
(808) 661-0191; Web site  

On Oahu:
at the Deli at He`eia Kea Pier, Kane`ohe, (open from 8 a.m. to 5 p.m. seven days a week)
(808) 235-2192
at the Ala Wai Small Boat Harbor Fuel Dock (open from 8 a.m. to 6 p.m. seven days a week) phone 955-8160
at Elmer’s Gliders and Sailplanes, Dillingham Airfield
(open from approximately sunrise / 6 a.m. to sunset / 6 p.m.)
at Rainbow Bay Marina, Pearl Harbor (military only; 9:30 am – 5:30 pm seven days a week):
(808) 473-0284
at Ko Olina Marina
(open 24 hours per day, seven days per week; requires credit card for purchase)
(808) 676-3348; Web site:
at Ke`ehi Marine Center, 24 Sand Island Access Road
(open weekdays, 8 a.m. – 3:30 p.m.; closed weekends;
min. purchase 20 gallons without a KMC fuel account)
(808) 845-6465; Web site
at Aloha 7-Eleven Waianae Mauka, 85-830 Farrington Hwy. Waianae, HI 96792
(808) 696-7244  

at Aloha 7-Eleven Kahaluu, 47-515 Kamehameha Hwy., Kahaluu, HI 96744
(808) 239-9983

Please note: Locations and hours are subject to change without notice.
It has been suggested that consumers call in advance of visiting any location to
get up-to-date instructions for purchasing small amounts of non-ethanol gasoline.

(This list last updated 11/09/09)



 Be mindful of these factors before you go on a long cruise or a great distance off shore. And you should be fully aware of general safety rules for handling and keeping fuel aboard your vessel. Inspect your fuel system on a regular basis:

  • as a boater, you should always be alert to the condition of your boat’s fuel system. For your safety and the welfare of your passengers, you should inspect your entire fuel system, including the inside of your fuel tanks, on a regular basis. Inspect your fittings and hoses, especially near the engine where heat and vibration can accelerate deterioration. Over time, those fittings, hoses, and even tanks can wear out;
  • the U.S. Coast Guard’s Boating Safety Circular 79 stated that “One of UL’s most startling findings was the fact that 23 percent of the owners of gasoline-powered boats continued to operate their boats after a fuel tank problem was detected, i.e., almost one-quarter of the owners of gasoline-powered boats responding to the survey do not fully comprehend the hazard of leaking fuel in the bilge of a boat.” If a fuel leak is detected, fix it immediately;
  • fire extinguishers are required on your vessel when a fire hazard could be expected from the motors or your fuel system. Make sure you have the right number and type of extinguishers, and that they are mounted properly, away from areas where a fire is likely to start such as the galley or the engine compartment;
  • gasoline engines installed in a vessel after April 25, 1940 (except outboard motors) must be equipped with an acceptable means of backfire flame control that is properly mounted and marked (USCG approved or compliant with SAE J-1928 or UL 1111 standards);
  • all vessels which use gasoline to generate electricity, or provide mechanical power or propulsion needs to be equipped with a ventilation system. If naturally ventilated, check to be sure ducts are unobstructed. For a powered ventilation system, make sure blowers installed in exhaust ducts are in working condition;
  • always carry a spare fuel filter or two aboard your vessel, so that if the filter becomes clogged while you are at sea, it can be replaced.

Before and during refueling:

  • close all ports, hatches and other openings;
  • extinguish all smoking materials;
  • turn off engines, electrical equipment radios, cellular phones, stoves and other appliances;
  • remove all passengers;
  • keep the fuel nozzle in contact with the tank;
  • portable fuel tanks should be refilled on shore.

After refueling:

  • wipe away any spilled fuel;
  • open all ports, hatches and doors to ventilate;
  • run the blower for at least four minutes following refueling;
  • check the bilges for fuel vapors before starting the engine;
  • do the sniff test and make sure there is no odor of fuel on the vessel. Your nose can be an effective gasoline leak detector;
  • never try to plug up a fuel tank vent. Without room to expand, the additional pressure could rupture fuel system components;
  • do not start your engine until all traces of fuel vapors are eliminated;
  • Remember the “One-Third Rule” by using one-third of your fuel going out, one-third to get back, and by keeping one-third in reserve;
  • be aware of the dangers of carbon monoxide.

In all cases, you should follow safe boating practices and make sure your vessel is always equipped with the required communication and safety devices to improve your chances of surviving an emergency situation.

  • if planning to venture more than one mile offshore, all recreational vessels (manually powered vessels excluded) are required to have a VHF radio or EPIRB;
  • make sure you have the right number and types of fire extinguishers. Inspect them regularly and recharge or replace them as needed;
  • a USCG approved, properly fitted and easily accessible personal floatation device (PFD) is required for every individual aboard while the vessel is underway. Children under 13 must wear their vest while on the water, even when anchored off shore. Children below deck or in an enclosed cabin are exempt;
  • equip your vessel with the proper, USCG approved, daytime and nighttime distress signal devices. Make sure they are clearly marked and readily accessible. Replace any safety equipment that has expired;
  • be sure navigation lights and other nighttime signaling devices are working properly, even if you don’t plan to be on the water after dark;
  • under certain circumstances, your vessel will be required to sound an audible signal. Know the requirements and properly equip your vessel with the right number and type of audible signaling devices (horn, whistle, bell);
  • get a Vessel Safety Check on a regular basis from the US Coast Guard;
  • file a float plan;
  • check the local weather before departing.

Be seen, be heard, be prepared…