The Best Fuel Options For Your Boat's Performance

Choosing the right fuel for your boat is essential for reliable performance and to avoid damage to your engine. The type of fuel you need depends on the make and model of your boat's engine, so it's important to check your owner's manual for specific recommendations. However, there are some general guidelines to consider when selecting fuel for your boat. Firstly, it is recommended to avoid fuel with high ethanol content (more than 10% ethanol) as it can cause corrosion and damage to your engine. Ethanol can also attract water, which can lead to issues with your fuel system. For this reason, ethanol-free fuel or fuel with a maximum of 10% ethanol (E10) is generally recommended for boats. The type of engine you have, such as gasoline or diesel, will also determine the best fuel for your boat. Gasoline engines typically use ethanol-free fuel or E10, while diesel engines use off-road diesel fuel. Additionally, the size and age of your boat can be a factor in fuel choice, with smaller boats often using gasoline and larger, commercial boats usually requiring diesel. It's also important to consider the octane rating of the fuel, as some high-performance engines may require a higher octane rating.

Ethanol-free gasoline

Ethanol-free fuel does not cause the corrosive effects associated with ethanol-containing gasoline. It ensures optimal performance and a longer lifespan for your boat's engine. However, it is more expensive than E10 or other ethanol-containing fuels. Additionally, it uses the octane enhancer additive methyl tert-butyl ether (MTBE) to produce cleaner exhaust, but combining it with ethanol from other fuel types can cause clogged fuel filters and performance issues. Therefore, it is crucial not to mix ethanol-free gasoline with other fuel types.

Ethanol, on the other hand, can cause serious damage to your boat over time. It can corrode rubber and fiberglass, leading to clogged fuel lines. It can also attract water into your fuel system through "phase separation," resulting in internal corrosion and uneven performance. Due to these issues, experts recommend draining ethanol-gasoline blends from your tank if your boat will be docked for more than 90 days.

Oil and gas mixtures

Before mixing oil and gas, it is important to check your owner's manual for the correct mixing ratio. Most modern boat engines have their own separate lubrication system, so oil-gas mixtures are not necessary. However, if you do have an engine that requires an oil-gas mixture, the mixing ratio will depend on the particular model. Common mixing ratios (gas:oil) include:

• 25:1 (usually during the break-in period)
• 50:1
• 100:1

To achieve these ratios, you will need to perform some basic calculations. For example, for a 50:1 gas:oil ratio, you will need to add 2.6 fluid ounces of oil per gallon of gas. For a 25:1 ratio, you will need to add 5.2 fluid ounces of oil per gallon of gas.

It is important to get the correct ratio of oil to fuel. Adding too much or too little oil can lead to a smoking motor, hiccuping performance at high RPMs, and even significant internal damage. Therefore, many boaters pre-mix their gasoline and oil before filling up their boat's tank to avoid an imbalance.

It is also important to use marine oil that meets the TC-W standard for 2-stroke engines. Marine oil, particularly oil from the original engine manufacturers, deals better with the demands of the marine environment due to the higher RPMs and proximity to water sources.

Marine gas oil

MGO is a distillate fuel, composed of blends of the evaporated components of crude oil during the distilling process, which are condensed from a gas state to a liquid state. It is similar to diesel fuel but has a higher density and does not need to be heated during storage. MGO is used in smaller to medium-high speed auxiliary units or motors and ship engines, such as those found on fishing boats, small ferries, or tugs.

MGO has a transparent to light colour and is marked with a red dye to prevent the misuse of cheap heating oil or MGO in inland shipping. MGO is more expensive than heavy fuel oil (HFO) and so HFO is still predominantly used in commercial shipping. However, due to the environmental impact of HFO, there are plans to limit its usage and move towards MGO in the future.

Diesel

However, diesel-powered engines will raise the price of a new boat significantly. In used boats, the costs to replace diesel engines are 2-6 times higher than those of comparable gas engines. Diesel engines are also notoriously more finicky than gas engines about what they ingest: air, fuel, coolants, and lubricants. That's worrisome when you consider that diesel repair costs are enormously higher than those for gas engines.

It would take decades to recoup the much higher initial and longer-term diesel costs via savings on fuel. If your boat's size dictates that you need a diesel-powered engine and you can afford one, then get one. But if you can get away with using gas, you'll probably come out ahead in the total cost of ownership.

Along with the EPA-mandated reductions in sulfur in diesel fuel, diesel engines themselves have gone through significant changes in the last 10-15 years. With the advent of technology like "common rail" ultra-high-pressure fuel injection systems and the addition of electronic engine controls and injection systems, diesels are emitting fewer emissions and performing better than ever.

Because diesel is more likely to be stored for longer periods of time than gasoline, it is also more likely to pick up water and other contamination along the way. Temperature change also impacts diesel fuel; it will tend to thicken in cold weather without additives. As part of the sulfur content reduction, the matter of the fuel's "lubricity" comes up. Diesel injection systems are designed and built to extremely close mechanical tolerances, so lubricity additives are a good idea.

Another property exclusive to diesel fuel is a phenomenon known as "waxing". In the US, there are two types of diesel fuel available: No.1, which is essentially kerosene, and No. 2, used for home heating and diesel engines. As seasons and temperatures change, fuel distributors alter their blends and additive ratios to help address this problem.

Biodiesel and biodiesel blends have become available in some parts of the US in the last 15 years. It can be made from a variety of sources, including used cooking oils, rendered animal fat, soybeans, and peanuts. While the green movement loves the idea, some studies suggest that the energy used to produce the fuel negates its claims for carbon footprint reduction. Biodiesel acts as a solvent and can loosen up any accumulated contaminants that typically settle in the bottom of your fuel tank. These will get pulled into fuel filters and may necessitate more frequent filter changes until things get cleaned out. That said, most engine manufacturers have approved the use of biodiesel blends, but it is of paramount importance to double-check your engine manufacturer's requirements before use.

Because of the enhanced probability of water ending up in your diesel fuel, a top-quality water-separating fuel filter is extremely important for any diesel engine. Filtering particulate matter is also important, but it's crucial not to overdo it. It's possible to create a scenario that will restrict fuel flow in your system, which will cause a "lean out" condition that can cause extensive damage.

Fuel stabilizers

There are several fuel stabilizer products available on the market, such as the Ethanol Shield Marine Fuel Stabilizer and STA-BIL Marine Fuel System Treatment. These products typically contain detergents and anticorrosive agents that help keep your engine and fuel system clean and protected. They can also help improve fuel performance and enhance gas mileage.

It is recommended to use a fuel stabilizer with every fill-up to ensure year-round protection for your boat. This is especially important if you plan on storing your boat for an extended period or if your boat is docked for more than 90 days. By using a fuel stabilizer, you can help prevent fuel-related issues and keep your boat in peak condition.

When choosing a fuel stabilizer, it is important to select a product that is compatible with your engine type and fuel system. Be sure to follow the manufacturer's instructions for proper usage and dosage. Additionally, it is always a good idea to consult your owner's manual or seek advice from a marine mechanic or professional if you are unsure about the best fuel and maintenance practices for your boat.

Frequently asked questions