The question is what speed will develop your boat with the electric-motorUnlike gasoline, where horsepower is the key, pound-thrust is the key, which is often confusing for beginners. Many expect instant planing, forgetting about the physical limitations of battery capacity and body design.
The real picture on the water is very different from the marketing promises of the manufacturers. Actual speed It depends on dozens of variables, from the state of the propeller to the density of the water and the direction of the wind, and understanding these nuances will allow you to avoid disappointment and correctly calculate battery life.
In this article, we will analyze in detail all the factors affecting the speed of the boat, and give specific figures that should be counted on when choosing a boat. electricYou will learn how to match the equipment for your tasks, whether it is quiet fishing in reeds or active movement in the reservoir.
Gravity vs. power: how to convert pounds into kilometers
The basic characteristic of any electric motor for a boat is thrust, measured in pounds (lbs), which is a static force that the motor can develop in place, not power on the shaft. kilometres It is impossible to use the formula directly, since the efficiency of the system is constantly changing.
But there is a rule of thumb that allows you to estimate the potential of an engine, which is that one pound of thrust can usually accelerate a properly loaded boat to 0.2-0.25 km/h under ideal conditions, which means that a 30 lbs motor can theoretically give a speed of about 6-7 km/h, but only if the weight of the boat is minimal.
It is important to understand that power-use It grows exponentially. To increase speed by just 1 km/h, the motor may need 30-40% more power, which is why the top speed on an electric motor rarely exceeds 10-12 km/h, as efficiency and battery life drop further.
Why not put powerful engines?
And it's not just because of the battery capacity that manufacturers limit electric motors, it's because of the design of the lower unit and the propeller, and when you're at high speeds, you get cavitation, which is boiling fluid, and you lose the propeller's thrust and it collapses quickly.
Effect of Boat Weight and Loading on Speed
Weight is the main enemy of speed on water, especially for electrical systems. Displacement regimeThe thrust system, which operates 95 percent of the boats with electric motors, is very restrictive, and every extra kilogram of cargo requires an increase in thrust, which directly reduces the final speed.
If you plan to take on board fishing equipment, sonar, navigator and passenger, the thrust reserve should be substantial. A lightweight PVC inflatable boat with one angler will show some results, and the same boat with two adults and a full trunk will show completely different results.
- 🚣♂️ PVC boat: Lighter, but has a soft bottom, creating greater hydrodynamic resistance at speeds above 5 km / h.
- ⚓ Metal boat: It is heavier on its own, but has a rigid body that holds the course better, but requires a more powerful motor to start.
- 🎣 Payload: Fishermen often underestimate the weight of anchors, cages with catches and canisters of water, which can make up up to 30% of the total weight.
There's a concept critical speed of displacement vesselThis is the limit beyond which a boat cannot accelerate, no matter how much power you add, without switching to planing. For electric motors, this threshold is usually 7-9 km / h depending on the length of the waterline.
The electric motor is not designed to plane heavy boats, but to move economically and quietly in displacement mode.
The Role of the Screw and the lower unit State
The propeller is the only element that transmits motor energy to water, and its state and geometry directly affect how fast your boat will travel, and even a small chip on the blades or overgrown with algae can reduce efficiency by 10 to 15 percent.
The screw's pitch determines how much water it throws away in one turn. Electric motors typically use small-step propellers optimized for low-speed propellers. Installing a large-step propeller can cause windings to overload and speed to fall due to inefficient operation.
⚠️ Attention: Never use propellers designed for gasoline engines on electric power without consulting the manufacturer. The difference in revolutions can lead to instant cavitation and engine failure.
Also, you should pay attention to the engine setup. The depth of the propeller should be optimal. If the motor is set too high, the propeller will capture air, creating noise and losing traction. If it is too deep, the resistance of the lower unit will increase.
Dependence of speed on battery charge
One of the main features of electrical systems is that the voltage drops as the battery goes down. At the beginning of the journey, when the battery is fully charged, the motor gives off maximum power and speed. terminal-stress falls.
This leads to the fact that 50% of the battery can produce not 12 volts, but 11.2-11.5 volts. The motor, trying to turn, consumes more current, but physically can not develop the previous power, as a result, the speed of the boat by the end of the fishing can be reduced by 1-2 km / h.
Use of lithium batteries (LiFePO4They keep the voltage more stable throughout the discharge cycle, providing a more stable speed compared to lead-acid counterparts.
Comparative table of speed and thrust
To make it easier for you to navigate the numbers, we have compiled a table with approximate speeds for a PVC boat 3.2-3.6 meters long with one angler (total weight about 200 kg), the data are averaged and can vary.
| Motor traction (lbs) | Max. speed (km/h) | Optimum speed (km/h) | Mode of work |
|---|---|---|---|
| 30 lbs | 5.5 - 6.0 | 4.0 - 4.5 | Small rivers, quiet water |
| 40 lbs | 6.5 - 7.0 | 5.0 - 5.5 | Reservoirs, wind up to 3 m/s |
| 50 lbs | 7.5 - 8.5 | 6.0 - 6.5 | Large water areas, current |
| 60+ lbs | 9.0 - 10.0 | 7.0 - 7.5 | Heavy boats, against the wind |
As you can see from the table, the increase in thrust gives a noticeable, but not linear, increase in speed. Increased thrust from 30 to 60 pounds will not double the speed, but will allow you to feel more confident in the wave and current.
For maximum efficiency, try to keep the speed in the range of 60-70% of the maximum power of the engine.
External factors: wind, flow and overgrowth
Water is a dynamic environment, and you can't ignore it. Headwinds or currents can completely offset the benefits of a powerful motor. If you have a 7 km/h motor, you'll only have 4 km/h of oncoming water at 3 km/h.
Overgrown boat hulls with algae or shells-fouling dramatically increases resistance. Smooth bottom slides on the water, rough - "plough" it, expending excess energy. Regular washing of the boat is not only a matter of aesthetics, but also a way to preserve the water. driving.
- 🌊 Excitement: At a high wave, the boat begins to prowl, the engine loses its focus, the speed drops.
- 🌬️ Side wind: Creates sailing, especially in high sides of PVC boats, requiring constant operation of the engine to hold the course.
- 🌡️ Water temperature: Cold water is denser than warm water, which theoretically gives a slightly better emphasis to the screw, but in practice this effect is minimal.
Also, take into account air temperature. Lithium batteries in the cold give off less energy, which can temporarily reduce the maximum power of the engine. Lead batteries in the cold also lose capacity, although they are less susceptible to sudden surges of voltage.
How to increase the speed of a boat with an electric motor
If you're not comfortable with your current speed, there are a few ways to improve things without buying a new engine: the first and most effective is to reduce weight, remove excess gear, use lighter anchors and batteries.
The second is to optimize landing, so you can distribute the load so that the boat runs smoothly on its keel, without any deferent on the bow or stern, and the skewed boat creates additional water resistance.
☑️ Check for maximum speed
The third option is to change the screws. If your motor allows you to change the screws, try the modified pitch model. However, do this carefully when controlling the temperature of the engine. You can also consider installing fairings on a lower unit, if the design of the motor allows it.
⚠️ Attention: Do not attempt to force the motor by removing the controller's limitations or using batteries with a voltage higher than nominal. This will overheat the windings and melt the insulation in minutes.
Remember, the electric motor is a tool for comfortable and quiet fishing, not for speed records, and its main advantage is the ability to stay on the water for a long time without noise and vibration, not high speed.
Frequently Asked Questions (FAQ)
Can an electric motor accelerate the boat to plane?
Most of the time, no. planing requires large power and special hull contours. Electric motors operate in displacement mode. Except for very lightweight one-man inflatable boats with powerful engines (80-100 lbs), but this is more of an exception.
Why is the engine humming, but the speed is falling?
It's likely that the screw was wound with algae or fishing line, or the screw was damaged (shattered blade), and the cause may be a discharged battery, which can not give the desired current.
Does the length of the boat affect the speed of the electric motor?
A longer boat has a longer waterline, which raises its theoretical speed limit in displacement mode, and a short boat will run faster into its speed barrier.
What is the most economical speed for an electric motor?
The most economical mode is considered to be a movement of 30-40% of power (about 3-4 km / h), in this mode, the energy consumption is minimal, and the battery life is maximum.
Do I need to heat up the electric motor before starting?
Technically, the electrical components do not need to be "warmed up"; however, in the cold season, it is recommended that the battery be kept warm to room temperature before use so that it gives up its full capacity.