Ethanol And Boat Engines: A Bad Mix?

Ethanol is a highly refined beverage (grain) alcohol added to fuel to reduce hydrocarbon emissions. It is often used as an oxygenate to help minimise air pollution. However, its impact on boat engines has been a topic of discussion and concern. While E10 ethanol fuel, which contains 10% ethanol, is commonly found at marinas, the question remains: is it harmful to marine engines?

Ethanol is a powerful solvent that dissolves fiberglass fuel tanks

Ethanol's solvent properties can lead to several issues in boat engines. Firstly, it dissolves fiberglass fuel tanks, fuel filters, and carburetors, causing damage to these essential components. Additionally, ethanol acts as a solvent for sludge while simultaneously dissolving polymers, which can lead to engine stoppage. This dual action of ethanol as a solvent can have detrimental effects on the engine's performance.

Another critical concern is ethanol's hygroscopic nature, meaning it attracts and absorbs water. Water condensation often forms in boat fuel tanks, and when ethanol absorbs this moisture, it can lead to water contamination or fuel phase separation, resulting in the engine stalling or even stopping altogether. This problem is exacerbated when ethanol gasoline is over 90 days old, as the aged ethanol further shortens the shelf life of the gas, making it more susceptible to absorbing water.

To mitigate the issues caused by ethanol in boat fuel, boat owners should follow several recommendations. Firstly, it is crucial to use fresh gasoline and avoid using ethanol gasoline that is over 90 days old. Secondly, adhering to the maintenance schedule, including regular cleaning of the carburetor and changing fuel filters, can help limit sludge build-up caused by ethanol. Additionally, proactive measures should be taken to address repetitive performance issues, such as draining and replacing the fuel with fresh gasoline, preferably 100% gasoline or ethanol-free gas.

In summary, ethanol's potent solvent properties, particularly its ability to dissolve fiberglass fuel tanks, can lead to significant issues for boat engines. Boat owners should be vigilant about the age and quality of their fuel and maintain their engines properly to minimize the detrimental effects of ethanol on their boat's performance.

Ethanol reacts with fuel filters and carburetors

Ethanol is a solvent that reacts with fuel filters and carburetors. It dissolves resins, rust, and dirt that have accumulated on older tank walls. This can cause filter-clogging and the formation of a mysterious gooey substance that will also clog filters.

Ethanol is also hygroscopic, which means it attracts water. Water from condensation often forms in the fuel tanks of boats. The ethanol attracts and absorbs the condensation. When this occurs, a boat engine may stop working due to water contamination or fuel phase separation.

• Never use ethanol gasoline that is over 90 days old. Ethanol shortens the shelf life of gas, and old gas is likely to absorb water and cause problems.
• Keep up with your maintenance schedule. Changing fuel filters and keeping your carburetor clean can limit the sludge build-up attributable to ethanol.
• Take care of problems immediately. Drain the fuel and replace it with fresh gasoline. If possible, get 100 percent gasoline. Ethanol-free gas is the best solution, but it is increasingly difficult to find.
• Use a quality fuel treatment for ethanol. When using an additive to counteract the effects of ethanol-treated gas, read labels carefully. Many additives for fuel contain ethanol or other alcohol products.

Ethanol attracts water, which can cause engine failure

Ethanol is hygroscopic, which means it has a tendency to attract water. This can be a problem for boat engines as water from condensation often forms in the fuel tanks of boats. When this happens, the ethanol attracts and absorbs the condensation. This can cause issues with the engine as the water contamination can lead to fuel phase separation.

Phase separation occurs when the ethanol and water in the fuel tank separate and form a distinct layer at the bottom of the tank. This layer is a corrosive mixture that can cause serious problems for marine engines. The upper layer of gasoline will be depleted of ethanol and have a reduced octane level, which can also impact the engine's performance.

To prevent phase separation, it is important to keep the fuel tank as dry as possible. This can be achieved by keeping the tank filled to prevent condensation. Additionally, using a fuel stabilizer and keeping up with regular maintenance can help to mitigate the effects of ethanol in boat fuel.

While E10 fuel (10% ethanol) is commonly used in marine engines, it is important to note that E15 fuel (15% ethanol) is not suitable for boat engines. E15 fuel can cause irreversible damage to engine and fuel system components, leading to engine failure and potential safety risks. Boat owners should always check the fuel pump label before fuelling to ensure they are using the correct type of fuel.

E15 gasoline is not suitable for use in marine engines

Firstly, E15 has not been approved for use in boat engines. Pumping E15 into a boat engine is, in fact, a violation of federal law. E15 has only been approved for use in 2001 and newer cars and light trucks. Boat engines have only been designed to use fuel with up to 10% ethanol, known as E10.

E15 has been shown to cause engine failure in boats. Testing by Mercury Marine revealed that several outboards tested on E15 showed signs of elevated piston and exhaust temperature, and some even failed. On the other hand, all of the outboards tested on E0 fuel (gasoline with no ethanol) completed the test without any issues.

The main issues with E15 in boat engines are lean operation and materials compatibility. E15 contains 5% oxygen by weight, compared to 3.5% for E10. This additional oxygen content leads to "enleanment" of the engine, causing an increase in exhaust gas temperatures. Unlike flex-fuel auto engines, marine engines cannot self-adjust to accommodate fuel with more than 10% ethanol.

The issue of materials compatibility is especially concerning for older, legacy engines. Ethanol is a harsh solvent, and the higher the concentration, the stronger its solvent properties. This can lead to corrosion and damage to fuel system components.

Furthermore, E15 fuel has a higher risk of phase separation, where ethanol attracts water into the fuel system through the fuel tank vent. This can result in internal corrosion, erosion of fiberglass, and uneven engine performance.

Therefore, it is clear that E15 gasoline is not suitable for use in marine engines. Boat owners should stick to using E10 or ethanol-free gasoline to avoid potential engine damage and performance issues.

Ethanol is not a fuel additive

Ethanol has been used as a fuel for centuries. In fact, around the turn of the 20th century, many early cars like the Model T were designed to run on straight ethanol fuel. However, times have changed and engines have become more advanced. There are now many studies showing that alcohol is harmful to a gas fuel system and engine, especially in the marine market.

E10 fuel, which contains 10% ethanol, is common throughout the United States and has been used in marine engines for over a decade. While it is not ideal, it is not necessarily bad for boat engines. In fact, after the transition period from non-ethanol fuel, E10 may actually be superior as it tends to keep low levels of water moving through the fuel system, keeping it dry.

However, ethanol does come with some problems and precautions. For example, ethanol is a powerful solvent that can dissolve fiberglass fuel tanks, fuel filters, and carburetors. It is also hygroscopic, which means it attracts water. This can lead to water contamination or fuel phase separation, causing the engine to stop working. To mitigate these issues, it is recommended to never use ethanol gasoline that is over 90 days old, keep up with maintenance, and use a quality fuel treatment that does not contain alcohol.

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