Ameer Randolph
The Yamaha 115 2-stroke engine has been reported to consume a significant amount of fuel. Users have reported fuel consumption rates of almost 3 gallons per hour at 1500 RPM, which is considered high for an engine of this type. At 3600 RPM, the engine burns about 8.5-8.7 gallons per hour, with speed numbers confirmed by GPS. The engine's fuel efficiency is also impacted by factors such as engine mounting, propeller design, and engine RPM, with higher RPM resulting in increased fuel consumption. When compared to newer 4-stroke engines, the Yamaha 115 2-stroke engine may use slightly more fuel, especially during extended periods of trolling. However, the exact fuel consumption rates can vary depending on various factors and operating conditions.
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What You'll Learn
Fuel efficiency at different RPMs
The fuel efficiency of a Yamaha 115 2-stroke varies depending on the RPM. At 1500 RPM, the engine should consume around 2 gallons per hour, while at 3600 RPM, the fuel consumption increases to about 8.5 to 8.7 gallons per hour. At 4000 RPM, the fuel efficiency ranges from 2.4 to 2.6 kilometres per litre, with a speed of approximately 38 kilometres per hour. As the RPM increases to 5000, the fuel efficiency stays above 2.2 kilometres per litre, and the speed increases to 50 kilometres per hour.
Some users have reported higher fuel consumption at lower RPMs, with one individual stating that their Yamaha 115 2-stroke used almost 3 gallons per hour at 1500 RPM. This discrepancy could be due to various factors such as engine settings, load, or other operating conditions.
When compared to newer engines, older 2-stroke engines are less efficient at low RPMs. A new DI 2-stroke or 4-stroke engine can offer significant improvements in fuel efficiency at trolling speeds. For example, while an older 2-stroke might use 22 gallons during a day of trolling and 2 hours at wide-open throttle (WOT), a newer engine might only use 21 gallons in the same scenario, resulting in a savings of over a gallon and a half.
Additionally, it's worth noting that engine RPM and fuel flow have a nearly linear relationship, meaning that as RPMs increase, fuel consumption also increases. This is evident in the comparison between a 120hp 2-stroke and a 175hp 4-stroke engine. At their respective WOT RPMs, the 2-stroke engine consumes 12 gallons per hour, while the 4-stroke engine consumes less at 16.9 gallons per hour.
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Fuel flow rate
The fuel flow rate of an engine is dependent on several factors, including engine design, mounting, and propeller characteristics. For a Yamaha 115 2-stroke engine, the fuel flow rate can vary based on these factors and operating conditions such as speed and load.
At 1500 rpm, the Yamaha 115 2-stroke engine typically consumes around 2 to 3 gallons per hour. However, some users have reported higher fuel consumption at this rpm, indicating potential variations due to specific engine configurations or operating conditions.
At 3600 rpm, the fuel flow rate increases to about 8.5 to 8.7 gallons per hour, with a speed of 30 mph. As the rpm increases further to 4000, the fuel efficiency ranges from 2.4 to 2.6 kilometers per litre, with an average load and a speed of approximately 38 km/hr.
At 4500 rpm, the engine can achieve a speed of 43 km/hr while maintaining a fuel efficiency of 2.4 to 2.5 km/litre. Pushing the engine to its maximum recommended rpm of 6150 results in a speed of 60 km/hr and a fuel efficiency of about 1.5 km/litre.
When comparing the Yamaha 115 2-stroke to other engines, such as a 130hp 2-stroke, the max fuel consumption of the Yamaha 115 2-stroke is specified as 49 litres at 5500 rpm in the service manual. This is lower than the 130hp engine's max fuel consumption of 56 litres at 5800 rpm, despite both engines sharing similar specifications in terms of displacement, bore/stroke, compression ratio, and dry weight.
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Fuel consumption vs horsepower
When it comes to fuel consumption versus horsepower, there are a few key points to consider. Firstly, let's look at the Yamaha 115 2-stroke engine as an example. According to user reports, this engine can burn around 8.5-8.7 gallons per hour at 3600 rpm, with a speed of 30 mph. At 4000 rpm, fuel efficiency can range from 2.4 to 2.6 kilometres per litre, with a speed of about 38 km/hr. During a 78-mile trip that included varying speeds, a Yamaha 115 2-stroke engine reportedly used 26.3 gallons of fuel, resulting in 2.96 miles per gallon.
Now, addressing the relationship between fuel consumption and horsepower, it is a common misconception that engines with higher horsepower ratings inherently consume more fuel. In reality, fuel consumption is influenced by various factors, including engine design, load, and operating conditions. Horsepower, as a measure of work accomplished, is determined by torque (force) and engine rpm (revolutions per minute). To produce higher horsepower, an engine requires greater combustive force, which is achieved by burning more fuel.
However, this does not mean that higher horsepower automatically translates to higher fuel consumption. The fuel efficiency of an engine depends on how effectively it can convert fuel into power. A larger engine may have a higher horsepower rating, but if it is not operating at its full potential, it may consume more fuel relative to its output compared to a smaller, more efficient engine. Additionally, a larger engine has to deal with increased internal friction and the burden of "lugging around" extra components, which can lead to wasted energy and reduced efficiency at low power.
On the other hand, a higher-powered engine that is run at a lower percentage of its maximum capacity may exhibit better fuel efficiency. This is because such engines have a margin of reserve power, allowing them to handle higher-than-anticipated loads without a significant increase in fuel consumption. Therefore, when selecting an engine, it is essential to consider not only the horsepower rating but also the anticipated load, operating conditions, and overall engine efficiency.
In summary, while higher horsepower may contribute to increased fuel consumption, it is not the sole determining factor. Fuel efficiency is influenced by a complex interplay of engine design, power output, load, and operating conditions. When comparing fuel consumption between engines of different horsepower ratings, it is crucial to hold variables such as load and resistance constant to ensure an accurate assessment.
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Fuel economy at different speeds
The fuel economy of a Yamaha 115 2-stroke engine varies depending on the speed and conditions. At 1500 RPM, the engine consumes about 2-3 gallons per hour, which is considered excessive by some users. At 3600 RPM, the fuel burn rate increases to around 8.5-8.7 gallons per hour, with a speed of 30 mph. As the RPM increases, the fuel consumption also tends to increase. For example, at 4000 RPM, the engine can deliver 2.4-2.6 kilometers per litre, with a speed of about 38 km/hr. At 5000 RPM, the fuel economy is above 2.2 km/litre, with a speed of 50 km/hr.
When it comes to real-world usage, the fuel efficiency of the Yamaha 115 2-stroke engine can vary based on different speeds and conditions. For example, during a 78-mile trip that included varying speeds, the engine consumed 26.3 gallons of fuel, resulting in a fuel economy of 2.96 MPG. Additionally, when trolling, a newer 2-stroke or 4-stroke engine can offer better fuel efficiency, reducing fuel consumption from one gallon to 5/8 of a gallon per day.
Comparing the Yamaha 115 2-stroke engine to other options, such as a 120hp 2-stroke engine at WOT, the Yamaha performs with slightly better fuel economy. The Yamaha achieves 3.03 MPG, while the 120hp engine delivers 2.8 MPG. However, when comparing the Yamaha to a 175hp 4-stroke engine, the Yamaha falls behind in fuel efficiency, with the 4-stroke engine achieving 3.97 MPG at 37 mph.
Overall, the Yamaha 115 2-stroke engine's fuel economy is sensitive to speed and conditions. While it may offer competitive fuel efficiency compared to other engines at certain RPM ranges, it is important to consider the specific usage patterns and requirements when making comparisons.
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Fuel usage compared to other engines
The Yamaha 115 2-stroke engine's fuel efficiency compared to other engines depends on several factors, including engine type, size, weight, and operating conditions. Here is a detailed comparison:
Yamaha 115 2-Stroke vs. Other 2-Stroke Engines
The Yamaha 115 2-stroke engine's fuel efficiency compared to other 2-stroke engines can vary. Some users have reported fuel efficiency of around 1 mpg with the Yamaha 115 2-stroke engine when operating at 3500-4000 RPM and speeds of 24 mph. In contrast, another user with a different 2-stroke engine reported better fuel efficiency of 2.96 mpg over a 78-mile trip, including a range of speeds. This indicates that fuel efficiency can differ even among 2-stroke engines, depending on specific engine characteristics and operating conditions.
Yamaha 115 2-Stroke vs. 4-Stroke Engines
When comparing the Yamaha 115 2-stroke engine to 4-stroke engines, there are some fuel efficiency considerations to make. Older 2-stroke engines were known to be inefficient at low rpms. However, newer direct injection (DI) 2-stroke and 4-stroke engines offer improved fuel efficiency at trolling speeds. For example, a user reported that their new DI 2-stroke engine consumed only 5/8 of a gallon during a day of trolling, whereas an older 2-stroke engine might burn a full gallon. Additionally, the newer 4-stroke engines may offer slightly better fuel efficiency at higher speeds. For instance, an older 2-stroke engine might use 22 gallons at wide-open throttle (WOT), while a newer 4-stroke engine might use 21 gallons, saving about a gallon and a half.
Yamaha 115 2-Stroke vs. Specific Engine Models
To provide a more detailed comparison, let's look at some specific engine models:
- Suzuki DF115A: The current model Suzuki DF115A weighs 187 kg, which is relatively close to the weight of the Yamaha 115 2-stroke. However, weight may not be a significant factor in fuel efficiency, as one user suggested that the difference in fuel burn between smaller engines is likely negligible.
- Suzuki 3x14x20: A user with a Suzuki 3x14x20 engine reported fuel efficiency ranging from 2.4 to 2.6 kilometers per litre at 4000 RPM, with speeds of about 38 km/hr. At higher RPM (5000), the fuel efficiency dropped to around 2.2 km/litre, and at WOT (6150 RPM), it further decreased to about 1.5 km/litre.
In summary, the Yamaha 115 2-stroke engine's fuel efficiency compared to other engines can vary depending on various factors. Newer 2-stroke and 4-stroke engines may offer improved fuel efficiency at trolling speeds, while specific engine models may have different fuel efficiency characteristics based on weight, RPM, speed, and other operating conditions.
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Frequently asked questions
A Yamaha 115 2-stroke burns almost 3 gallons per hour at 1500 rpm.
The maximum fuel consumption of a Yamaha 115 2-stroke is 49L at 5,500 rpm.
At 3600 rpm, a Yamaha 115 2-stroke burns about 8.5 to 8.7 gallons per hour.
The fuel consumption of a Yamaha 115 2-stroke when cruising is about 2.96 MPG.
