Why You Should Avoid Ethanol Fuel in Boats

Updated November 12, 2024

When you invest in a boat, taking good care of it becomes essential. Routine maintenance is important, but so is the type of fuel you use. In the marine world, it’s highly recommended to avoid ethanol-blended fuel, but finding ethanol-free gas is becoming more difficult. Let’s explore the drawbacks of using ethanol fuel in boats and the concerns with additives.

What is Ethanol Fuel?

Ethanol is essentially highly refined alcohol, made from natural sources like corn, sugarcane, or wheat. It’s added to gasoline to reduce costs. The three main fuel types you’ll encounter are:

E0: 0% ethanol
E10: 10% ethanol, 90% gasoline
E15: 15% ethanol, 85% gasoline

Why is Ethanol Bad for Boat Engines?

Though ethanol-blended fuels are common, they can be harmful to your boat’s fuel system and engine. Two major issues with ethanol are phase separation and component deterioration.

Phase Separation

When water enters your fuel tank, it bonds with the ethanol in the fuel. Over time, the water-ethanol mixture separates from the gasoline and sinks to the bottom of the tank. This can lead to serious engine damage if that mixture gets into your motor. Since ethanol is hygroscopic, it absorbs moisture from the air, making phase separation more likely, especially in humid or marine environments.

Deterioration

Boats with fiberglass fuel tanks are at risk because ethanol can break down the resins holding the tank together. The resulting debris can clog your engine. Ethanol doesn’t just harm fiberglass; it can also deteriorate rubber, plastic, and even some metals—all materials found in your fuel system. While some boaters use additives to combat ethanol’s effects, this method can be tricky and unreliable.

Impact on Performance

Another drawback is that ethanol contains less energy per gallon than pure gasoline, so ethanol-blended fuel can decrease your boat’s power and fuel efficiency. You may find that you need to refuel more often, which can increase your overall operating costs.

Cold Weather Issues

In colder climates, ethanol presents an additional risk. Water absorbed by ethanol can freeze in the fuel lines or tank, potentially causing cracks or other damage to the system during storage in the off-season.

The Downsides of Fuel Additives

Fuel additives, which have been around for a while, are used to boost octane or preserve fuel for long periods. Recently, additives have been developed specifically to treat ethanol-blended fuel, but they come with their own problems.

First, there are many different types of fuels across the country, all refined differently by major oil companies. It’s unlikely that every additive has been tested with every type of fuel. Would you risk using chemicals that might not be compatible with the fuel in your multi-thousand or even million-dollar boat? No additive can fully stop phase separation or fix a fuel tank once separation occurs.

Water Contamination Risks

Because ethanol readily absorbs water, the risk of water contamination in the fuel is much higher compared to non-ethanol fuel. This contamination can be harmful to the engine, leading to poor performance, stalling, and costly repairs.

Benefits of Using Non-Ethanol Fuel

Because ethanol-blended fuel is so widespread, many boat and engine manufacturers claim their products can handle E10 gas. But the long-term effects are still uncertain. To protect your investment, consider using non-ethanol fuel (also called REC 90). Here’s why it’s a safer choice:

More Energy: Non-ethanol fuel provides over a third more energy than ethanol, which translates to better fuel efficiency.
Less Crop Dependency: It reduces our reliance on crop production for fuel.
Longer Shelf Life: Non-ethanol gas has a longer shelf life, making it ideal if you don’t use your boat regularly.
Lower Water Contamination Risk: By using non-ethanol fuel, you lower the chances of water being absorbed into the fuel, reducing phase separation risks.
Better for Winter Storage: E0 is less likely to freeze or cause fuel line damage in colder temperatures.
Marine Refueling Stations: Refuel at marine stations. They typically offer the right type of gas for boats, lowering the risk of ethanol-related damage.
Pump Check: Always double-check the pump to ensure you’re getting non-ethanol gas. Some stations offer E10 or E15, and blender pumps can mix fuels containing ethanol.

Stabilizers as a Short-Term Solution

If you can’t avoid ethanol-blended fuel, using a high-quality fuel stabilizer can help reduce the risk of phase separation in the short term. Stabilizers are particularly helpful if your boat will sit unused for long periods. However, even with stabilizers, it’s crucial to drain and replace old fuel regularly, as no stabilizer can fully eliminate the risks associated with ethanol.

Regular Inspections & Maintenance

Routine inspections and maintenance of your fuel system are critical, especially when using ethanol-blended fuel. This includes checking fuel lines, filters, and tanks for signs of wear and damage caused by ethanol. Early detection of problems can prevent more severe engine issues later on.

Fuel System Upgrades

If you own an older boat with a fiberglass or other ethanol-sensitive fuel system, consider upgrading to newer materials designed to withstand ethanol’s corrosive effects. Modern fuel systems use components made from ethanol-resistant materials such as certain plastics and metals.

Protect Your Boat by Avoiding Ethanol-Blended Fuel

In summary, while ethanol-blended fuels may appear convenient, they can lead to serious long-term damage to your boat’s engine and fuel system. To ensure the best performance and avoid costly repairs, choose non-ethanol fuel whenever possible. Your boat’s health and longevity depend on it.