The Power Of Racing Gas In Boats

Mixing racing gas with regular gas in a boat is a complex issue that depends on several factors, including the type of engine, the octane rating, and the presence of ethanol in the fuel. It is crucial to refer to the owner's manual for specific recommendations regarding the appropriate type of fuel for your boat's engine. The manufacturer's guidelines will provide insights into the fuel that will enable your engine to achieve its peak performance.

The type of engine in your boat plays a significant role in determining the suitable fuel. For instance, a 2-stroke outboard engine typically requires a mixture of gas and oil, while newer engines, such as 4-stroke engines, obtain lubrication from oil in the crankcase and may not need oil mixed into the gas. Additionally, the octane rating of the fuel is essential, with most smaller recreational boat engines performing well on 87 octane, while some higher-horsepower engines may require higher octane fuel, such as 89 or 91.

Another critical consideration is the presence of ethanol in the fuel. Ethanol can cause moisture absorption, leading to potential service issues. Therefore, it is generally recommended to avoid using fuel with ethanol in boats, especially if the engine is older and not designed to tolerate it. In such cases, ethanol-free fuel or marine-grade fuel with appropriate additives to protect valves and reduce carbon deposits may be preferable. However, it is worth noting that not all marine fuel is ethanol-free, and the availability of ethanol-free options may vary by region.

In summary, when considering mixing racing gas with regular gas in your boat, it is essential to consult the owner's manual, understand the specific requirements of your engine, and take into account factors such as engine type, octane rating, and the presence of ethanol in the fuel. Proper fuel selection is crucial to ensure optimal performance and maintain the health of your boat's engine.

Octane ratings and engine performance

Octane ratings are a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand before detonating. The octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates its resistance to detonating under pressure without a spark.

Whether a higher octane fuel improves or impairs an engine's performance depends on the design of the engine. In general, fuels with a higher octane rating are used in higher-compression gasoline engines, which may yield higher power for these engines. The added power in such cases comes from the way the engine is designed to compress the air/fuel mixture, and not directly from the rating of the gasoline.

Fuels with lower octane ratings are ideal for diesel engines because diesel engines (also called compression-ignition engines) do not compress the fuel but rather compress only air and then inject fuel into the air that was heated by compression. Gasoline engines rely on the ignition of a compressed air and fuel mixture, which is ignited only near the end of the compression stroke by electric spark plugs. Therefore, being able to compress the air/fuel mixture without causing detonation is important mainly for gasoline engines. Using gasoline with lower octane than an engine is built for may cause engine knocking and/or pre-ignition.

The octane rating of aviation gasoline was extremely important in determining aero-engine performance in the aircraft of World War II. The octane rating affected not only the performance of the gasoline but also its versatility; the higher octane fuel allowed a wider range of lean-to-rich operating conditions.

In spark-ignition internal combustion engines, knocking (also known as knock, detonation, spark knock, pinging, or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from the propagation of the flame front ignited by the spark plug. Instead, one or more pockets of the air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only and at a precise point in the piston's stroke. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle.

Knocking should not be confused with pre-ignition, as they are two separate events. However, pre-ignition is highly correlated with knock because knock will cause a rapid heat increase within the cylinder, eventually leading to destructive pre-detonation.

Most modern engine management systems have a knock sensor that monitors if knock is being produced by the fuel being used. In modern computer-controlled engines, the ignition timing will be automatically altered by the engine management system to reduce the knock to an acceptable level.

The octane number is the simple average of two different octane rating methods—motor octane rating (MOR) and research octane rating (RON)—that differ primarily in the specifics of the operating conditions. The higher the octane number, the more stable the fuel. Retail gasoline stations in the United States sell three main grades of gasoline based on the octane level:

• Regular (the lowest octane fuel, generally 87)
• Midgrade (the middle-range octane fuel, generally 89–90)
• Premium (the highest octane fuel, generally 91–94)

Some companies have different names for these grades of gasoline, such as unleaded, super, or super premium, but they all refer to the octane rating. The large number on the yellow gasoline pump octane label is the minimum octane rating. The (R+M)/2 Method on the label refers to the octane testing method used, where R is Research Octane Number and M is Motor Octane Number.

The standard means of testing octane is with an octane testing engine. This test is similar to the way the mass of an object can be determined by comparing it to objects (references) of known mass on a balance scale. Primary Reference Fuels (PRF) of precisely known octane are formed by combining iso-octane, heptane, and other well-known standards such as toluene. These PRFs are used to bracket a given fuel sample to determine the pressure at which similar knock intensities are observed. This measurement is taken by adjusting the octane engine's cylinder height, which changes the compression ratio/pressure in the engine until the knocking reaches a specific intensity level.

The (R+M)/2 you see on the label refers to the average of the research octane number (RON) and the motor octane number (MON) ratings. To determine the RON, the fuel is tested under engine idle conditions with a low air temperature and slow engine speed. To determine the MON, the fuel is tested under the more stressful conditions of higher air temperature and engine speed.

Ethanol in boat fuel

Ethanol is a very high-proof alcohol made from products like corn, sugar cane, or wheat that is added to fuel. It is an "oxygenate" that helps reduce hydrocarbon emissions when added to fuel to reduce air pollution.

Ethanol-blended fuel is labelled as E10, E15, or E85, which refers to the percentage of ethanol in the fuel. E10, a blend of 10% ethanol and 90% gasoline, is the most common type of ethanol-blended fuel and is used in both automobiles and boats.

While E10 gasoline generally works well in internal combustion engines, it can cause issues in boat engines if left stagnant. Over time, the ethanol portion of the fuel can absorb water molecules and separate from the gasoline, sinking to the bottom of the fuel tank. This is known as phase separation. Running an engine with phase-separated fuel can result in performance issues such as misfiring, bad starting, poor compression, and overall sub-optimal performance.

Additionally, the watery ethanol gas can damage plastic fuel lines, rubber gaskets, and certain types of fiberglass fuel tanks. Therefore, it is recommended to use E10 or lower ethanol-rated fuel in boats and to avoid E15 fuel, as it is not recommended by the boating industry due to potential engine issues.

It is also important to note that ethanol fuel mixtures can lead to engine damage, especially in older boat engines built before 1990. To avoid issues, it is recommended to either empty the fuel tank completely or run the boat at least every 60 days.

In summary, while ethanol-blended fuel can be used in boats, it is crucial to use the appropriate type of fuel and to take precautions to avoid phase separation and potential engine damage.

Fuel stabilizers

Chemically, a fuel stabilizer is formulated from petroleum products, including a mixture of lubricants and antioxidants. They are designed to optimize fuel performance, contributing to enhanced gas mileage and improved engine power. They also prevent corrosion, which is the bane of any boater's existence.

There are several reliable brands of fuel stabilizers on the market, including:

• Sta-Bil
• Quicksilver Quickstor
• West Marine EZ-Store EZ-Start
• Star Tron Enzyme Fuel Treatment
• Yamalube Fuel Stabilizer and Conditioner Plus
• BioborEB Ethanol Buster
• ValvTect Ethanol Gasoline Treatment

When choosing a fuel stabilizer, consider the following:

• Does the product make realistic claims?
• Is the treat rate reasonable?
• How long has the manufacturer been in business?

It is also important to follow the instructions for use. For example, for STA-BIL Marine Fuel System Treatment, users are instructed to pour the product directly into the fuel tank prior to filling up, using 1 oz for every 10 gallons of fuel, and then running the engine for 5 minutes to treat the entire fuel system.

Fuel requirements for different boat engines

The fuel requirements for your boat engine will depend on the type of engine in your boat. The first step in determining the right fuel for your boat is to consult the owner's manual for the engine. The manufacturer will provide the most accurate information about the type of fuel your boat engine requires.

Gasoline Engines

Gasoline engines are far more common in pleasure craft than diesel ones. Gas boats run on the same gas as cars, but there are some details about the type of gas to avoid.

Diesel Engines

Diesel boats run on the same fuel as diesel cars (#2 diesel fuel). Diesel-powered boats offer increased torque and horsepower compared to similarly-sized gasoline engines. They are also more fuel-efficient. However, diesel engines are more expensive than gasoline engines, and the cost of replacing a diesel engine is 2-6 times higher than that of a gasoline engine. Diesel engines are also more particular about what they ingest, including air, fuel, coolants, and lubricants. As such, diesel repair costs are significantly higher than those for gasoline engines.

2-Stroke vs 4-Stroke Engines

Two-stroke engines complete a power cycle in just two strokes (one up and one down) of a piston, while four-stroke engines, commonly found in modern passenger cars, complete a power cycle in four strokes (one up, one down, one more up, and one more down).

Two-stroke outboard motors usually require oil to be mixed with the fuel for lubrication. A special oil is required for this, and it must be mixed according to the manufacturer's recommended ratio to avoid engine damage. Modern 2-stroke outboards may have an oil reservoir and pump system that automatically supplies the required oil-gas mixture to the engine.

Four-stroke engines, on the other hand, get their lubrication from oil in the crankcase, similar to a car engine.

Ethanol in Gasoline

Most marine engines are designed to operate safely on fuel with no more than 10% ethanol (E10). Using fuel with a higher ethanol content, such as E15 or E85, can void the manufacturer's warranty and cause severe damage to the engine. This is because ethanol blends higher than 10% can have corrosive effects on the fuel system components. Additionally, ethanol attracts water, which can lead to water settling out of the fuel and causing issues with the engine.

Experienced boat owners typically prefer to use ethanol-free fuel (E0) whenever possible. If E0 is not available, E10 fuel is acceptable.

Octane Rating

The octane rating of the fuel you use will depend on the specific requirements of your engine. Most engines will run fine on 87 octane, but some higher-horsepower engines may require a higher octane, such as 89 or 91. Check your owner's manual to determine the recommended octane rating for your boat engine.

Fuel Sources

When fueling your boat, it is recommended to use fuel from a marina as they offer gas that is safe for all boat types, including ethanol-free options. While marina fuel may be more expensive, it will help ensure your engine runs optimally and avoid costly repairs in the long run.

If marina fuel is not accessible, you can fill up your gas cans at a gas station. Look for a \"rec blend\" or recreational blend label, which indicates fuel without ethanol.

Where to buy boat fuel

The best place to buy fuel for your boat is at a marina. Marinas offer fuel that is safe for all boat types, including ethanol-free options. While marina fuel can be more expensive than filling up gas cans at a local gas station, it's worth paying a little extra to ensure your boat's engine runs efficiently.

If you don't have access to a marina, you can fill up your gas cans at a gas station. Look for a "rec blend" or "recreational blend" label, which indicates that the fuel contains no ethanol. Ethanol-free fuel is important for boat engines, as ethanol can draw moisture, leading to service issues and potential water damage.

Before fuelling up, it's crucial to know your boat's fuel requirements. Check the owner's manual to determine the recommended fuel type and octane level. Most newer recreational boats have similar fuel requirements, but older boats or those with 2-stroke outboard engines may need a fuel mixture of gas and oil.

Additionally, be mindful of safety practices when fuelling your boat. Know your boat's fuel tank size, listen for the distinct sound of a tank nearing fullness, and avoid topping off the tank. These measures will help prevent accidental fuel spills, which can be costly and harmful to the marine environment.

Frequently asked questions