When a newcomer to water tourism or fishing first encounters the technical specifications of a boat, he is often baffled by the abundance of abbreviations. One of the most common searches in search engines is the phrase "plm decoding the motor," and this is not accidental. Understanding the basic terminology is the first step to a competent choice of equipment that will last for many years and will not fail on the water.
abbreviation outboard motor It reads simply and logically: Outboard outboard motor.It's a device that attaches itself to the transom of a boat, a boat or a yacht, and it's used to propel a vessel. Unlike stationary engines, which are built into the hull, outboard models are mobile, easy to remove for transportation and maintenance, and it's this versatility that has made them the most popular around the world.
Inside the category outboard motor There's a huge world of engineering, from compact two-strokes for inflatable boats to powerful four-stroke units that develop the speed of a racing car, and every boating needs to understand the nuances of design, fuel system and control, so as not to overpay for unnecessary functions or, conversely, not to buy a too weak unit.
Historical context and evolution of outboard motors
History of creation outboard It's been around for over a century, and in that time, technology has gone from primitive internal combustion engines to high-tech electronic systems. The first prototypes were made in the late nineteenth century, but the real breakthrough was Cameron Waterman's invention in 1903, whose engine weighed only 27 kilograms, which was a revolution for the time, allowing the engine to be installed on light wooden boats.
For a long time, the industry has evolved towards greater power and reliability, and if models require constant attention, mixing oil with gasoline by hand, and often cleaning candles, then modern models require constant attention. outboard motor They became the model of autonomy, the emergence of electronic fuel injection systems, such as EFI The Electronic Fuel Injection (EFI) has dramatically changed the way we operate, making starting the engine as easy as turning a key in a car.
Today, the market is divided by several giants, such as Yamaha, Mercury, Tohatsu and SuzukiAnd Chinese brands, in turn, are actively adopting modern technologies, offering affordable alternatives. outboard motor It helps to understand why modern engines require less maintenance, but are more expensive to purchase.
Design features and principle of operation of outboard motor
Outwardly. outboard It's a monoblock with a few key units that are all connected by a single body. The top part, called a lower unit, contains the internal combustion engine itself, the ignition system, and the carburetor or injector. Below is a lower unit leg, inside of which is a shaft that transmits torque to the propeller, and this whole structure is attached to the trunk of the boat using a rod or a bolt connection.
The most important element is the cooling system, and in the vast majority of cases, it is used. flow-coolingThe nasak takes water from the reservoir, and it circulates around the hot parts of the engine, removing heat, and then it is thrown back through the control hole, which makes the engine dependent on the presence of water: categorically do not run outboard motor on land without connecting to the external water supply system, as this will lead to instant overheating and jamming of the piston group.
The transmission of rotation to the screw is through a gearbox, which also performs the function of reducing the speed. The engine can rotate at a speed of 5000-6000 rpm, while the optimal screw works more efficiently at 4000-5000 rpm. The gearbox provides this balance, allowing the motor to develop maximum power without destroying the screw.
The motor can be controlled in a variety of ways, with low power using a rump, a pen attached to a lower unit, which changes the direction of thrust and the position of the throttle. outboard motor Remote control is used via cables (machine) or electronic systems (drive-by-wire), when the control levers are placed on the console of the boat, and the engine responds to electrical signals.
Two-stroke and four-stroke engines: eternal confrontation
When choosing outboard motor The customer always has to ask about the tact of the engine, which is a fundamental difference in terms of weight, fuel consumption, noise and maintenance costs. Two-stroke engines (2T) run on a mixture of gasoline and oil, and they have one cycle per crankshaft, which makes the structure easier, lighter and cheaper, but fuel consumption is higher, and the exhaust is more smoky and toxic.
Four-stroke engines (4Ts) are a car engine, with a separate stroke for intake, compression, combustion and exhaust, and the oil in them is in the crankcase and does not burn with the fuel. They are quieter, 20-30% more economical and more environmentally friendly, but they are much heavier than their two-stroke counterparts of similar power and more difficult to repair due to the presence of a valve mechanism and an oil pump.
The choice between them depends on the tasks. For fishing in the cast, where silence is important, or for long transitions, where fuel is important, there is no alternative. 4T For hunting, where the boat often has to be carried by hand, or for use as a spare engine, 2T They are not competitive because of their low weight.
- 🐟 For fishing: Four-strokes are preferred due to the lack of vibrations and low noise levels that can scare the fish.
- 🏔️ For mountain rivers: Two-strokes benefit from the ability to work in any position and ease of repair in the field.
- ⚖️ By weight: two-stroke engine with a capacity of 5 hp weighs about 20-22 kg, while a four-stroke engine of the same power will pull 25-27 kg or more.
Modern technologies blur the boundaries: there are two-stroke engines with direct injection (for example, the engine is not designed for the first time). E-TEC from Johnson/Evinrude or OptiMax Mercury, which combines the lightness of 2T with the efficiency of 4T, although their maintenance requires high qualifications.
When buying a used four-stroke engine, be sure to check the color of the oil. If it is black and thick, the engine is likely to have a large load or piston problems.
Criteria for the power selection and length of lower unit
Power outboard motor It's not just a horsepower number, it's a balance between speed, fuel consumption and boat load capacity, and there's the idea of maximum recommended power for a particular hull, and exceeding that liment is dangerous, because the boat can lose stability, bury its nose in a wave, or get structural damage to the transom.
The length of the lower unit (legs) of the motor must strictly correspond to the height of the transcent of your vessel. S (Short) - 381 mm (15 inches) L (Long) 508 mm (20 inches) and X (Extra Long) — 635 mm (25 inches) If the leg is too short, the screw will trap air (cavitation), which will lead to loss of speed and overheating. Too long a leg will increase water resistance and the risk of hitting the bottom.
It's also important to consider the type of propeller. The screw's pitch affects traction and top speed. Heavy boats and trolling require small pitch propellers, high-speed gliders require large pitch propellers. Many manufacturers offer the possibility of replacing the propeller, which allows fine-tuning. outboard motor under specific operating conditions.
☑️ Checklist before buying an engine
Fuel, oils and maintenance
Durability outboard It depends on the quality of fuels (fuels and lubricants). For two-stroke engines, the use of special oils with the labeling is critical. TC-W3The usual engine oil for cars in the 2T engine will lead to the formation of soot on candles and the exhaust windows.
Four-stroke engines require high-quality automotive oil, but with marine conditions in mind. FC or FDThe oil change intervals in 4T engines are usually 50-100 hours or once a season, depending on the model.
Special attention should be paid to conservation for the winter period, residues of water in the cooling system can freeze and break the cylinder block, so after the last release in the season, the procedure of "reconservation" or simply draining the water and storing it in heat is mandatory.
| Parameter | Two-stroke (2T) | Four-stroke (4T) | Electromoto |
|:--- |:--- |:--- |:--- |
| Fuel. | Gasoline + Oil | Gasoline (AI-92/95) | Electricity |
| Weight. | Light | Heavy | Medium/Severe (with battery) |
| Noise. | High | Low | Silent |
| Service | Simple | Difficult (oil change) | Minimum |
| Environmental friendliness | Low | Medium | High |
What is a motor running and why is it needed?
Running is the process of working out the rubbing parts of the engine. In the first hours of operation (usually 5-10 hours of motor time), you can not give full gas. You need to work at different turns to make the piston rings rubbish against the cylinders. Neglect of running in reduces the life of the engine by 2-3 times.
Typical malfunctions and methods of their elimination
Even the most reliable outboard motor It can fail. Most often, it's power or ignition. If the engine doesn't start, the first thing to check is for sparks and fuel. A clogged carburetor is a common disease of motors that have been stuck with gasoline for a long time. Modern injection systems are less prone to this, but require clean fuel.
Overheating is another common problem: If the control hole stops running water, immediately shut down the engine. The reasons may be that debris enters the water intake, breaks the pump impeller or breaks the rubber insert in the thermostat. Regular visual inspection of the water jet is a mandatory habit of a boater.
Problems with the gearbox are manifested in the form of a hum or vibration. Often this indicates that water enters the gearbox through the coils. Checking for the presence of an emulsion (white slurry) in the gearbox oil should be done regularly. If there is an emulsion, you need to replace the gums and oils.
Timely replacement of anodes (metal plates) on lower unit prevents electrochemical corrosion of aluminum engine parts in salt water.
Safety of operation in water
Operation outboard motor It requires strict safety regulations, and it is a requirement to have a safety check on the operator's wrist, and if a person falls overboard, the check is pulled out and the engine dies, preventing the screw from hitting the person or the boat from moving around uncontrolledly.
It is also important to monitor the fuel level and not to allow work to the limit in shallow water conditions. A screw hitting a stone or a driftwood can break the lower unit or even tear the engine apart. In such situations, the use of cut pins or special safety screws that break on impact, saving the gearbox is recommended.
⚠️ Attention: Never try to start the engine if you smell the gas vapor in the cockpit. Spark from a starter or magneto can cause a fuel vapor explosion.
⚠️ Attention: When reversing, be extremely careful: the steering on many PLMs works inversely or less efficiently, and the review is closed by lower unit.
Prospects for the development of boat technology
The future of the industry outboard motor It's in the hybridization and electrification plane, electric motors are getting more powerful and batteries are lighter, and in quiet lakes and protected areas where ICE is banned, electric veins are becoming the standard, but for longer distances and harsh conditions, gasoline and diesel units will hold the palm for a long time.
Digitalization of control allows the motor to be integrated into a single vessel network (NMEA 2000), displaying all data on the navigation screens. Remote diagnostics via smartphone is already becoming a reality for top models, allowing notifications of low oil levels or overheating in real time.
Frequently Asked Questions (FAQ)
Can I use 95 octane gasoline in a outboard motor?
Yes, most modern four-stroke engines can use the AI-95. For two-stroke engines, it is important that gasoline does not contain alcohol (ethanol) in high concentrations, since it can destroy rubber seals and carburetors. It is better to use a quality AI-92 from proven gas stations.
How often should I change the oil in the outboard motor gearbox?
The gearbox oil is recommended to be changed once a season or every 100 motor hours. When changing, pay attention to the color: silver oil is the norm, black oil is wear and white (emulsion) water.
What to do if the engine sinks?
If the motor has been underwater for a short time, it needs to be washed with fresh water, take out the candles, blow out the cylinders and pour the oil, then try to start. If the engine has been lying on the bottom for a long time (especially in salt water), most likely, major repairs or replacement will be required, as irreversible corrosion processes have begun.
What is the difference between a lower unit foot and a lower unit foot?
The terms are often confused in everyday life: lower unit is the part of the hull through which the shaft passes, and the bottom of the outboard motor itself, where the gearbox and the screw are located, is correctly called the "bottom section" or simply "leg," although many refer to the entire motor as "lower unit" by analogy.