Modern water motors no longer present their leisure without electrical equipment: sonars, navigators, GPS trackers and electric motors require stable power supply.
The issue of autonomy becomes critical, especially when hiking for many days or long fishing, when shore charging is not available.
This is where the stage comes in. power-drivenIt is capable not only to push the boat, but also to replenish the battery charge, ensuring the operation of all onboard electronics.
However, many owners of equipment make fatal mistakes, relying on myths about “powerful charging” in basic configurations.
Let’s see how the charging system works, what Yamaha or Tohatsu They really know how to charge the battery, and what to do if the standard current is not enough.
How to charge in outboard motors
The principle of operation of the power supply system in outboard motors is based on the conversion of the mechanical energy of rotation of the crankshaft into electric.
Inside the motor, under the flywheel, located stator-coil (generator), which when the magnets rotate produces alternating current.
Further, the current passes through the rectifier-regulator, where it is converted to constant and stabilized to a voltage safe for the battery.
It is important to understand that basic models of two-stroke motors are often equipped with lighting coils, designed solely to power headlights or small lamps, and not to charge batteries.
The power of such systems usually does not exceed 3-5 Amps, which is critically low for restoring the capacity after the sonar.
⚠️ Warning: Attempting to charge a deeply discharged AGM or GEL battery with current from a weak lighting coil can lead to plate sulfation and battery failure.
Four-stroke motors, as a rule, have a more advanced system, resembling an automobile one, with a separate alternator and a full voltage regulator.
Here the charging current can reach 10–16 Amps, which already allows you to comfortably serve the onboard network.
Why is the generator not working at idle speed?
The flywheel magnets must rotate at a certain speed to create a sufficient electromagnetic field. At idle (800-1000 rpm), the EMF induction is not enough to overcome the battery voltage, so the charging is not physically going.
Two-stroke vs. four-stroke: where is the most current?
Choice between two-stroke and four-stroke The engine is often dictated by its budget and weight, but from an electric point of view, the difference is enormous.
Two-strokes are cheaper and lighter, but their electric part is often an "Achilles heel" for fans of outdoor activities with gadgets.
In most cases, a two-stroke engine with a capacity of up to 15 hp has a coil that produces only 2-4 Ampere.
This means that in an hour of full-gas operation, you will return to the battery as much energy as a GPS sonar consumes in 15-20 minutes.
For powerful two-stroke engines (from 25 hp and above), the situation is better: there are often installed coils for 6-10 Amps, but this may not be enough for powerful electric motors.
- ⚡ Two-stroke engines up to 15 hp - charging is weak (2-4A), suitable only for maintaining a charge.
- ⚡ Four-stroke engines from 5 hp - have a full charge (6-10A and above).
- ⚡ Electrical starters are always more powerful in terms of generation than models with manual starters.
Four-stroke units, such as Honda BF20 or Suzuki DF15They are equipped with alternators similar to automotive alternatives.
They are capable of delivering a stable current even at medium speeds, making them ideal for boats saturated with electronics.
Table of compatibility and charging power
To avoid guessing whether your engine will have enough power, let’s turn to specific numbers.
Below are the averaged data on popular models that will help plan an upgrade.
| Motor model | Type | Generator power (A) | Appointment |
|---|---|---|---|
| Yamaha 2FMHS (2bhp) | two-stroke | 0 (no reel) | Only traction. |
| Tohatsu M5BDS (5 hp) | two-stroke | ~3-4 A | Weak support |
| Yamaha F9.9JMHS (9.9bhp) | four-stroke | ~6-8 A | Basic charging |
| Suzuki DF60ATL (60 hp) | four-stroke | ~16-22 A | Active charging |
| Mercury 115 Pro XS | four-stroke | ~25-35 A | Powerful network |
As you can see from the table, low-power two-strokes are practically useless as a source of energy.
If you plan to install LiFePO4 battery capacity of 100 Ah to power the electric motor, a regular engine generator 9.9 hp may not be enough for its full charging for a day of fishing.
Connection Schemes: How Not to Burn Electronics
Proper connection is the key to the long life of your equipment.
The most common mistake is the direct connection of the generator wires with the battery terminals without a fuse.
The charging circuit must be present. safety-fuse Or a smooth insert.
Its nominal value is selected based on the maximum current of the generator, but not less than 10-15 Amps for small motors and 20-30 Amps for powerful ones.
The wire cross section also plays a role: 2.5 mm2 is enough for currents up to 10A, but for powerful systems it is better to use 4 mm2 or more to avoid a voltage drop.
⚠️ Warning: Never turn off the battery when the engine is running! At the time of a circuit break, the voltage in the on-board network can jump to 100 or more volts, which instantly kills the rectifier-regulator and connected appliances.
The connection circuit is as follows: the output of the generator (usually a yellow or white wire) goes through the fuse on the positive terminal of the battery.
The mass of the generator must be securely connected to the motor body or the negative terminal of the battery.
To check the availability of charging, you can use a voltmeter by connecting it to the battery terminals.
When the engine is running, the voltage should be in the range 13.5-14.8 Volts.
☑️ Checking the charging system
Low power problem and external generators
What if you have a great two-stroke engine 15 hp, but its generator barely pulls the sonar?
There are two ways to solve this: upgrade the stator or install an external source.
The stator upgrade is possible on some popular models (for example, Yamaha or Tohatsu), where you can replace the standard coil with a reinforced version from a more powerful engine of the same series.
This requires disassembly of the engine and skills in working with electricity, but gives a "native" solution without unnecessary wires.
The second option is to install a gasoline generator in the boat's hazelnut.
Modern inverter generators weighing 10-12 kg are capable of producing 1-2 kW of energy, which allows charging the battery with a powerful charger (20-30 Amps) and even powering household appliances.
This solution is ideal for multi-day expeditions, where the count goes to kilowatts.
- 🔋 Installation of an additional stator is difficult, but neat and reliable.
- 🔋 The gas generator is noisy, but very powerful and versatile.
- 🔋 Solar panels are quiet, but depending on the weather and the time of year.
Use DC-DC chargers. If you're installing a gasoline generator or a powerful solar panel, plug them in through a smart charger (DC-DC), which has a charging profile for your battery type (AGM, GEL, Lithium), which will extend the battery life at times.
Maintenance of the charging system
Regular maintenance of the electric part of the motor is often ignored, and this leads to problems at the most inopportune time.
The first thing to check is the status of the contacts and terminals.
In conditions of high humidity and salt water, oxidation occurs very quickly.
Once a season, you need to remove the terminals, clean them to shine and lubricate them with a special lubricant for electrical contacts.
It is also worth inspecting the wires for rubbing, especially in the exit points of the engine pallet and near the tiller.
Vibration is the main enemy of wiring, so all harnesses must be securely secured by clamps.
Checking the rectifier-regulator is carried out by a multimeter in the diode check mode.
If the engine is warmed, and there is no charging, or vice versa - there is a recharge (voltage above 15V), most likely, this particular unit is faulty.
Replacing the regulator is a simple procedure, but requires a precise selection of the model for a specific motor.
Regularly cleaning the contacts and checking the belt tension (if any) or the state of the stator coil will prevent 90% of electrical problems on the water.
Frequently Asked Questions (FAQ)
Can I charge the car battery with a outboard motor?
Yes, you can if the motor is equipped with a generator of sufficient power (usually 10A and above), but car starter batteries (WET) are not designed for deep discharge, unlike traction batteries, and you need to charge them carefully, keeping track of the level of the electrolyte.
Why doesn’t the motor charge the battery at idle speed?
At idle speeds, the speed of the flywheel magnets is not sufficient to produce EMFs that exceed the battery voltage. To start charging, it is usually necessary to raise the speed to 2000-2500 rpm and above.
Which wire is better to use to connect charging?
Use only copper polycore wire in insulation resistant to oil and gasoline (for example, KG or special boat wires).
Do you need a separate safety lock if you have it in the engine?
Yes, an additional safety lock in the circuit, directly at the battery, is required, and it will protect the boat from fire in the event of a short circuit of the wire going from the motor to the battery, if the insulation is damaged.