Maximum power
The maximum operating power of the outboard motor, expressed in kilowatts.
The practical value of motor power is described in detail in “Maximum power" is higher. Here we note that the kilowatt (derivative of watt) is just one of the units of power used in fact along with horsepower (hp); 1 HP ≈ 735 W (0.735 kW). Watts are considered the traditional unit for electric motors (see "Engine Type"), but for a number of reasons, outboard motor manufacturers use this designation for gasoline models as well.
Maximum revolutions
The highest shaft speed that the outboard motor is capable of developing.
Theoretically, the speed of rotation of the propeller (or turbine — see "Motor type") depends on the engine speed, and, accordingly, the speed that the boat is capable of developing. However, in addition to this indicator, many other factors also affect the performance of the motor — engine power (see above), gear ratio (see below), propeller design, etc. As a result, situations are quite normal when a more powerful and high-speed motor has lower revolutions than the weaker one. Therefore, this parameter is, in fact, a reference one, and has almost no practical value when choosing. Unless it can be noted that high-speed motors are more susceptible to noise and vibration than low-speed ones; however, this moment can be compensated by the use of various technical tricks.
Capacity
The working volume of a gasoline outboard engine (see "Engine type"). This term usually means the total working volume of the cylinders.
The larger this value, the higher the motor power, usually (see the relevant paragraph). At the same time, with an increase in the working volume, fuel consumption, weight and dimensions of the unit also increase; and power depends not only on this indicator, but also on a number of other factors — ranging from the number of strokes (see "Engine duty cycle") or the presence of turbocharging (see below) and ending with specific design features. Therefore, situations are not excluded when a smaller engine will have more power, and vice versa.
Piston stroke
The working stroke is the distance between the two extreme positions of the piston in a gasoline (see "Engine type") outboard motor. In most cases, this parameter is purely reference; situations where such data is really needed are extremely rare — usually during the repair or maintenance of the engine.
Fuel tank volume
The total volume of the fuel tank provided in the design or delivery set of the outboard motor (depending on the type of tank — see "Fuel tank").
The larger the capacity of the fuel tank, the longer the engine will be able to work without refueling, the less often it will be necessary to replenish the fuel supply in the tank. On the other hand, volumetric tanks have appropriate dimensions and weight, especially when filled; the latter is especially critical for motors with built-in tanks (see above).
Recommended fuel
The type of gasoline recommended for use in an internal combustion engine outboard (see "Engine Type"). In fact, this paragraph indicates gasoline with the lowest octane rating that is allowed to be used in the engine; higher rates are allowed, lower ones are highly undesirable, if not outright prohibited.
The octane number is an indicator that determines the resistance of a particular brand of gasoline to detonation (self-ignition during compression in the cylinder). Detonation is a very undesirable phenomenon, because. it leads to an increase in engine loads simultaneously with a decrease in its power and an increase in the amount of harmful substances in the exhaust gases. And this phenomenon occurs in cases where the engine uses gasoline with lower octane numbers than those for which the unit is designed.
Automobile gasoline, which is also used for refueling boat engines, is marked with the AI or RON index; the first option is used in the characteristics of east european motors, the second — in foreign ones. However, in both indexes, the number after the letters means the octane number. The higher this number, the more demanding the engine is on fuel quality. Thus, for example, a unit under AI-92 will be able to work normally with AI-95, but AI-90 or AI-87 cannot be filled into it. "Record holders" for unpretentiousness today are engines that can work even on the AI-76; but they are a rare exception to the general rule.
Gear ratio
The gear ratio describes how fast the propeller of the outboard motor rotates relative to the speed of rotation of its shaft. For example, a gear ratio of 2 means that for each revolution of the shaft, the screw, in turn, makes two revolutions (that is, it rotates twice as fast). In modern outboard motors, this parameter, in fact, is purely reference, because. the practical characteristics of the unit (power, traction, etc.) depend on many design features and are practically not related to the gear ratio.
Weight
The total weight of the outboard motor. This parameter is indicated, usually, only for the unit itself, without taking into account the fuel in the tank and the tank itself (if it is external, see "Fuel tank"), as well as additional equipment. Motor weight data can be useful in order to estimate the overall balance of the boat and the change in its payload capacity.
