Comparison Parsun F5BMS vs Hidea HDF5HS

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.

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.

The design of the exhaust system in a gasoline outboard motor (see “Engine type”), more precisely, the method of exhaust gases used in this system.

— Above the screw. This category includes two types of engines. The simplest option is when exhaust gases are emitted directly into the air. Such systems are extremely simple and cheap, but the exhaust can create a noticeable inconvenience for people in the boat (not only because of the gases, but also because of the rather high noise level); therefore, they are found only in the simplest outboard motors, and even then quite rarely. A more common option is to release exhaust gases into the water above the propeller (most often through the so-called anti-cavitation plate — a flat ledge above the propeller). Such systems are more comfortable than "air" ones, while they are simpler and cheaper than propeller exhaust (see below), although they are still considered less technically advanced.

— Through the screw. In systems of this type, the exhaust is led into the water directly through the propeller hub; in fact, the position of the exhaust pipe coincides with the axis of rotation. This reduces the noise level compared to systems using exhaust over the propeller, and also slightly increases power and traction characteristics. The downside of these advantages is the design complexity and, accordingly, the high cost.

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).

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.

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.