Planning a water trip or a serious fishing trip always starts with a question about fuel supplies. Beginners often get lost in guessing how much gasoline or diesel will go to overcome a distance of 100 kilometers. However, in a water-motor environment, operating mileage is not always correct due to the variability of water conditions. Fuel consumption It depends on many factors that are not present when driving.
Unlike a paved road, the water surface is constantly changing its specifications, and wind, wave, flow and algae fouling of the bottom all make adjustments to the water surface. fuel-efficiency yours outboardThat's why experienced water-engineers prefer to count the cost per litre per motor hour rather than per kilometer, but to understand the real fuel needs, we still have to link these numbers to distance.
In this article, we will discuss how to calculate the real needs of fuel for your Yamaha, Mercury or TohatsuWe're going to look at the effect of engine power, propeller type and driving style on the final figure in the gas station check, and understanding these processes will help you avoid the unpleasant situation of being far from shore and empty.
Why it is difficult to count liters per 100 km on water
The main problem of calculation fuel-flow If you can keep a constant speed of 90 km/h on the highway, even with full gas, the boat speed will "walk" on the water, which makes the standard formula "liters divided by kilometers" extremely inaccurate for navigational calculations.
The main enemy of efficiency is the resistance of water, which grows exponentially, not linearly. motor-power It's not used to increase speed, but to fight the wave and to resist the aerodynamics. The cost may increase significantly, although the speed will increase slightly.
And you can't ignore the current factor. You'll have to go 50 kilometers against the current and 50 kilometers downstream, and you'll have to spend different amounts of time and fuel, even though the distance traveled is the same. track-speedNot just the speedometer.
⚠️ Warning: Never plan a route based on the boat's top speed. The actual cruising speed at which best efficiency is achieved is usually 70-75% of the maximum.
The way that professionals do this is to use the concept of a motor clock, which is the engine's load time, and by knowing your average engine consumption per hour and your planned speed, you can determine the fuel supply with high precision.
Factors affecting the appetite of the outboard motor
The final figure in liters is influenced not only by engine size, but also by a combination of technical and operational parameters. Understanding these factors will help you reduce operating costs. floater.
- 🚤 Boat loading: Each additional passenger or kilogram of cargo requires more power to get on plane, which dramatically increases gasoline consumption.
- 🌊 Underbody condition: The bottom overgrown with seashells or algae creates additional resistance, forcing the motor to work in a more intense mode.
- ⚙️ Spinning pitch: Incorrectly selected screw does not allow the engine to reach optimal speeds, which leads to either overspending or overheating.
Two-stroke engines that burn a mixture of gasoline and oil are traditionally considered less economical, but modern direct-intake models (E-TEC, OptiMax) can be more efficient than older four-strokes. Four-stroke engines (four-stroke) gain in economy at low and medium speeds, but lose in weight.
We should not forget about the technical condition. fuel-systemContaminated carburetor chicks or faulty injector injectors disrupt the mixing, which directly hits the owner's wallet. Regular maintenance is the key to predictable consumption.
Calculation method: from motor clocks to kilometers
To understand how much fuel is going to be consumed per 100 kilometers, we need to do two things: figure out the flow rate per hour and find out the average speed. (Flow per hour / Speed) * 100But let's get the details.
Average statistics petrol-engine It consumes about 250-300 grams of fuel per 1 horsepower per hour at full load. However, on cruising mode (about 3,500-4000 rpm), this figure decreases. For a rough calculation, you can use the rule: a two-stroke engine burns about 300-350 g / hp / h, and a four-stroke engine burns about 200-250 g / hp / h.
Calculation nuances for different conditions
If you're going against wind and wave, your speed will drop and your flow rate will stay the same or increase, and then the flow rate per 100 km of travel can increase by 30-40% compared to the calculated calm. Always lay a reserve.
So let's take an example: you have a boat with a 15 hp engine, you're going on a plane at 35 km/h, and the engine consumption in this mode is about 4.5 liters per hour, divisible 4.5 by 35 and multiplied by 100, and you get about 12.8 liters per 100 km, and that's the value that's relevant for this particular environment.
Comparative flow table for popular capacity
The following are averaged data for calm water glitch modes, and the actual numbers may vary depending on the type of boat (PVC or aluminum) and load.
| Engine power (hp) | Type of engine | Average consumption (l/hour) | Average speed (km/h) | Consumption per 100 km (l) |
|---|---|---|---|---|
| 5 hp | two-stroke | 1.5 - 2.0 | 20 | 7.5 - 10.0 |
| 9.9 hp | two-stroke | 3.0 - 3.5 | 30 | 10.0 - 11.6 |
| 15 hp | four-stroke | 3.5 - 4.5 | 35 | 10.0 - 12.8 |
| 30 hp | four-stroke | 8.0 - 10.0 | 45 | 17.7 - 22.2 |
| 50+bhp. | four-stroke | 15.0+ | 55+ | 27.0+ |
As you can see from the table, with increasing power, the absolute consumption increases, but the speed increases. However, after a certain threshold (usually about 40-50 km / h for light boats), further acceleration requires a disproportionate amount of energy, and the speed increases. efficiency falls.
The optimal economical speed for most PVC boats and small boats is in the range of 30-40 km / h. Exceeding this threshold leads to a sharp increase in fuel consumption.
How the driving style affects the tank
Boat control is a variable that you control completely. booster The carburetor or the injector enrichment system, which is necessary for acceleration, but it's destructive for economy.
The smooth addition of gas allows the boat to get on plane at minimal cost. Trying to keep the boat in transition mode for a long time (when the nose is already raised, but there is no planing yet) is the most inefficient way of moving. frontal resistance Maximum, but slow speed.
- 🛑 Avoid "twitching": Constant change of turns knocks down the mixing settings and increases the appetite of the engine.
- 👀 Look ahead: Slow down before the excitement or obstacles, so that you do not have to gas sharply to restore inertia.
- 🌬️ Use the wind: On small engines, it is sometimes more profitable to go a little slower, but in the wind, than to fight the elements at full throttle.
Proper heating is also important. Cold-stroke two-stroke engines require a richer mixture. Long-term idle operation without load also consumes fuel, albeit in smaller volumes than full gas.
Secrets of fuel economy at long distances
If you want to travel as far as possible on your fuel supply, you need to optimize all the parameters. propellerIf the blades have chipped or burrs, the efficiency of the screw drops. Even a slight deformation of the edge can increase the flow rate by 5-10%.
The second important aspect is the distribution of the load: shifting the center of gravity to the nose or in the stern changes the angle of the trim, and properly loading it allows the boat to go more easily into the plane and keep its course stable, which reduces the load on the engine. Experiment with moving passengers and tanks.
☑️ Checklist of economical navigation
⚠️ Attention: Using fuel-saving additives in outboard motors is a controversial method, and many of them can disrupt the oil lubrication properties of two-stroke engines, leading to piston group bullies.
Finally, don't forget the aerodynamics. If you keep a boat with a windshield or awning installed, make sure that they don't create a sail that inhibits movement. Sometimes, taking off the awning at full speed gives you a tangible boost in speed or fuel economy.
Use a GPS tracker or track-enabled navigator to show you your actual track speed and distance, allowing you to accurately calculate the actual flow rate after each trip.
Two-stroke vs. four-stroke: who is more economical?
The eternal water-motor dispute, traditionally held to be two-stroke motors (two-stroke) less economical, because some of the fuel mixture just goes into the exhaust. This is true for carburetor models of the old type. Evinrude E-TEC or Mercury OptiMax) changed the rules of the game.
Four-stroke engines (four-stroke) They're famous for their low- and medium-speed efficiency, they don't require mixing oil with gasoline, which is also a form of economy (oil is expensive), but they have a minus-weight, and a heavy motor on a light boat can require more energy to get on plane, offsetting savings on cruising speed.
The critical factor is the age of the technology: A modern two-stroke direct injection can be more economical than the old four-stroke, but in the middle class (5-15 hp) four-stroke engines win in costs by 20-30% if properly operated.
Frequently Asked Questions (FAQ)
Is it true that a four-stroke engine is always more economical than a two-stroke?
Not always. At full speed, the difference can be minimal. However, when idling and trolling, a four-stroke uses significantly less fuel, because it doesn't lose the mixture through the exhaust. Also, you don't have to buy a separate oil for the mixture.
How much does the wave affect fuel consumption?
The impact can be enormous. On high waves, the boat is constantly hitting the water, losing speed. To maintain planing, you have to add gas. The consumption can increase by 1.5-2 times compared to calm.
Should I buy a bigger engine to save money?
Paradoxically, yes, sometimes it does. A 15 hp engine on a heavy boat will run to the limit, consuming a lot of fuel. A 20 hp engine will run half-heartedly (at optimal revs) and may be more economical, albeit more expensive to buy.
Which gasoline is better to pour for savings: 92 or 95?
If the engine requires 92nd gasoline, filling the 95th will not give you power gain or savings, since the kalyl number of candles and ignition settings are designed for a certain octane number. In some cases, using a higher octane on carburetor engines can even worsen combustion.