The Power Behind Boats: Choosing The Right Gasoline

Choosing the right type of gas for your boat is essential for optimal performance and the longevity of your boat's engine. The type of gas you need depends on the type of engine you have. The owner's manual will provide you with the recommended fuel type and octane rating. Using the wrong fuel can lead to engine damage and reduced performance. Marine gas is a specialized fuel that burns cleaner and cooler than regular gas, making it ideal for boats. It contains additives that help prevent corrosion and engine deposits. Marine fuel is typically a blend of gasoline, diesel, or ethanol. Marine diesel oil (MDO) and marine gas oil (MGO) are the two most common types of marine fuel, with MDO being used in large ships and MGO in smaller boats. Another type of marine gas is ethanol-blended fuel, which is becoming more popular due to its environmental benefits but is not suitable for all boats.

Gasoline vs diesel

When it comes to choosing between gasoline and diesel for your boat, there are several factors to consider, including performance, maintenance, cost, and environmental impact. Here's a detailed comparison to help you make an informed decision.

Performance

Gasoline engines are typically found in smaller boats and offer high performance. They can run at higher revolutions and are often preferred for their ability to deliver greater power relative to the weight of the engine. Gasoline engines are ideal for achieving faster speeds and are commonly used in racing and pleasure boats.

On the other hand, diesel engines excel in torque and are known for their ability to push large loads at low RPMs. This makes diesel a preferred choice for larger boats, as they can provide the necessary power to move heavier vessels efficiently. Diesel engines generally have better fuel efficiency than gasoline engines, allowing for longer trips without refuelling.

Maintenance

Maintenance requirements differ between gasoline and diesel engines. Modern gasoline engines are computer-controlled, reducing maintenance needs. Gasoline engines are generally considered easier to service, and there is a wider availability of mechanics and parts for these engines.

Diesel engines, while known for their longevity, may require more specialised maintenance and repairs. The parts for diesel engines tend to be more expensive, and mechanics often charge higher labour rates. However, diesel engines have a reputation for requiring fewer major repairs over their lifespan.

Cost

The upfront cost of a diesel engine is typically higher than that of a gasoline engine. Diesel engines are heavier and more expensive to produce, which is reflected in the purchase price. Additionally, the maintenance and repair costs for diesel engines tend to be higher.

However, when it comes to fuel costs, diesel engines may offer some savings. Diesel fuel often has a lower price per litre at the pump, and diesel engines are generally more fuel-efficient. This means that, over time, a diesel engine may offset some of its higher upfront costs through reduced fuel expenses.

Environmental Impact

The environmental considerations of gasoline and diesel engines are also worth noting. Gasoline engines have improved significantly in terms of emissions and are now equipped with catalytic converters, making them cleaner-burning options.

Diesel engines produce less carbon monoxide than gasoline engines, which is an important safety consideration, especially for boats with enclosed spaces. However, diesel exhaust can produce sulphur dioxide, which can cause nausea. Additionally, diesel engines are known for their distinct odour, which may be unpleasant, especially at low vessel speeds.

The choice between gasoline and diesel depends on various factors, including boat size, intended usage, performance requirements, and budget. Gasoline engines are ideal for smaller boats, racing, and pleasure craft, offering high performance and easier maintenance. Diesel engines, on the other hand, are better suited for larger boats, providing the necessary torque and fuel efficiency for heavier vessels. Consider your specific needs and preferences to make the right choice for your boating experience.

Ethanol-free gasoline

Firstly, ethanol is a powerful solvent that can dissolve fiberglass fuel tanks, as well as react with fuel filters and carburetors. This can lead to costly repairs and engine issues. Additionally, ethanol attracts water, which can result in water contamination or fuel phase separation, causing the boat engine to stop working.

By using ethanol-free gasoline, boat owners can avoid these potential issues. This type of fuel is typically available at busier marinas and service stations near popular boating locations, such as lakes and rivers. While it may be slightly more expensive, it can save money in the long run by preventing engine problems.

For older boats, particularly those over 15 years old, ethanol-free fuel is especially important. Older boat engines may not tolerate any ethanol at all and can be prone to leaks in fiberglass fuel tanks when exposed to E10 fuel. Therefore, it is crucial for owners of older boats to choose ethanol-free options whenever possible.

To summarize, ethanol-free gasoline is the preferred choice for boat owners due to its compatibility with various engine types and its ability to prevent issues caused by ethanol, such as corrosion and water absorption. While it may be slightly more expensive and less readily available, the benefits of ethanol-free gasoline make it the recommended option for optimal boat performance and longevity.

2-stroke vs 4-stroke engines

Overview

The main difference between 2-stroke and 4-stroke engines is in their design. A 2-stroke engine completes its power cycle (intake, compression, combustion, exhaust) in two strokes of the piston, while a 4-stroke engine requires four strokes to complete the same cycle. This makes 2-stroke engines simpler, smaller, and lighter, but also less fuel-efficient and more polluting.

Pros of 2-Stroke Engines

• Simpler design with fewer moving parts, making them easier to repair
• Smaller and lighter, improving power-to-weight ratio and acceleration
• More affordable
• Require less maintenance, with fresh oil added every time the fuel tank is filled

Cons of 2-Stroke Engines

• Less fuel-efficient, consuming more fuel and requiring more frequent refuelling
• Produce higher emissions, burning and releasing engine oil along with the fuel
• Louder and less pleasant to hear
• Less durable, with a less effective lubrication system

Pros of 4-Stroke Engines

• More fuel-efficient, with fuel efficiency up to 50% better than 2-stroke engines
• Produce far fewer emissions, with modern 4-stroke engines running up to 90% cleaner
• Quieter and produce less vibration
• More durable due to heavier weight and lower RPMs
• Better torque, making them suitable for heavier boats

Cons of 4-Stroke Engines

• More complex design with more moving parts, requiring regular maintenance
• Larger and heavier, compromising acceleration and top-end speed
• Require regular oil changes and filter replacements

Choosing the Right Engine

When choosing between a 2-stroke and a 4-stroke engine, it's important to consider factors such as affordability, fuel efficiency, power, emissions, durability, and ease of maintenance. For smaller boats, a 2-stroke engine might be preferred due to its lightweight and acceleration capabilities. However, for larger boats or long-distance travel, a 4-stroke engine is more suitable as it is more fuel-efficient and has better torque. Additionally, if emissions and environmental impact are a concern, a 4-stroke engine is the better choice.

Marine gas oil (MGO)

MGO is formulated to burn cleaner and cooler than regular automotive gas, making it ideal for marine engines, which operate at lower RPMs. It also contains additives that help prevent corrosion and engine deposits, prolonging the life of the engine. The density of MGO is usually close to 860 kg/m3 (at 15°C), and it has a sulphur content between 0.10 and 1.50 m/m %. This makes it a low sulphur fuel oil or LSFO, which is important for meeting emissions regulations in Emission Control Areas (ECAs).

MGO is also known as bunker fuel or bunker oil, referring to the fuel storage tanks on vessels and marinas. It meets the ISO-F DMA specifications and the sulphur limit required for European ports. When using MGO, it is important to monitor the temperature of the fuel system and ensure it does not drop below 2 CST or exceed 20 CST. Additionally, MGO should be stored separately from other fuel grades to avoid contamination and mixing.

MGO is a more expensive option than heavy fuel oil, but with increasing environmental concerns and stricter emissions regulations, the use of MGO is expected to become more prevalent in the years ahead. Engine technology in shipping is also anticipated to adapt to accommodate the use of MGO.

Marine diesel oil (MDO)

MDO is widely used by medium-speed and medium/high-speed marine diesel engines, as well as larger low-speed and medium-speed propulsion engines that typically burn residual fuel. It is a heavy fuel oil used in large ships, while marine gas oil (MGO) is a lighter fuel used in smaller boats.

MDO is made through a catalytic cracking and visbreaking refinery process. Catalytic cracking breaks large molecules into small molecules at high temperatures with an appropriate catalyst. Visbreaking, on the other hand, turns the bottom product of the vacuum unit, which has extremely high viscosity, into a lower viscosity, marketable product through a mild thermal cracking operation. The amount of cracking is limited to safeguard heavy fuel stability.

The market for MDO is much smaller than on-highway diesel. According to 2004 US diesel fuel sales statistics, marine shipping only accounts for 3.7% of the total diesel market. This is due to the high proportion of petroleum residue, which makes it suitable for large marine engines.

MDO has been criticised for its high sulphur content, with values ranging from 1 to 4.5 percent by mass for different grades. As a result, many countries and organisations have established regulations and laws governing its use. For example, the International Maritime Organization's (IMO) MARPOL convention is the most widely adopted international convention covering the prevention of operational or accidental pollution of the marine environment by ships.

Frequently asked questions