Comparison Vorskla PMZ 4000 vs Fisher 32

The type of engine is determined by the power source that the outboard motor uses during operation.

— Petrol. Internal combustion engines running on gasoline (diesel options are not used among boat engines for a number of reasons). Such engines are quite difficult to maintain and are expensive both in themselves and in operation (due to the high cost of fuels and lubricants). In addition, they have a large weight and dimensions, and are also considered non-environmental due to the fact that they are quite noisy and create exhaust gases during operation. However, all these shortcomings are covered by a number of advantages — first of all, the ability to create high-power units suitable for even the fastest ships, as well as the suitability of such engines to work with generator systems (see below). Also note that keeping a supply of fuel with you for refueling is usually easier than carrying spare batteries or looking for a source of electricity to charge the battery every time. Gasoline are divided into 2-stroke and 4-stroke.

— Electric. Motors powered by electricity — most often, a car battery or other battery of a similar class is used for power. Such units are distinguished by a low noise level and the complete absence of exhaust gases, which allows them to be used even in those reservoirs where "gasoline traction" is prohibited for environmental re...asons. They are also lighter and simpler in design than gasoline, and electricity is much cheaper than fuel. However, powerful electric motors would require too large and heavy batteries. Therefore, this principle is only suitable for low-power motors designed for small boats (or for use as auxiliary ones on more “serious” vessels, but again, not very large ones). As a result, most modern electric motors are fairly simple and inexpensive devices of modest power, designed mainly for situations in which a petrol engine is poorly suited for one reason or another — for example, when driving on the “protected” reservoirs mentioned above, or hunting / fishing, when noise is undesirable.

The duty cycle of the petrol engine (see "Engine type") installed in the boat.

— Duplex. Two-stroke engines have a good ratio of volume and useful power, besides, they are simpler in design and cheaper than four-stroke ones. On the other hand, they have a rather high fuel consumption and noise level, and gasoline and oil must be filled not separately, but as a mixture. Such a mixture must correspond to certain proportions, otherwise the engine will either wear out and heat up due to a lack of oil, or smoke due to its excess. However high-end motors can use automatic mixing systems (see below), eliminating the need for the user to manually prepare the mixture. However, even when perfectly proportioned, two-stroke engines burn a certain amount of oil along with gasoline, which is why they are considered dirtier than four-stroke engines.

— Four stroke. For the same working volume, four-stroke engines tend to have less power than two-stroke ones. They also require compliance with specific transportation rules. However, this is offset by a number of advantages — primarily relatively low noise levels and gasoline consumption. In addition, gasoline and oil are refueled separately into the engine — this is more convenient and economical than preparing a mixture; and during normal operation, the lubricant practically does not burn out, which also has a positive effect on the environmental frien...dliness of the engine. At the same time, such units are quite expensive, as a result of which the four-stroke cycle is typical mainly for premium outboard motors.

The maximum operating power of the outboard motor, expressed in horsepower.

Horsepower (hp) has traditionally been used primarily to refer to the power of internal combustion engines, including gasoline engines (see "Engine type"). However, in outboard motors, these units are also used for electric models (see ibid.). This is due to the fact that the majority of gasoline engines are on the market, and boat manufacturers prefer to indicate the maximum recommended engine power in “horses”.

The general patterns when choosing outboard motors in terms of power are as follows. On the one hand, a more powerful unit will allow you to develop more speed and is better suited for a heavy boat (see "Maximum boat weight"). On the other hand, weight, dimensions, cost and fuel/energy consumption also directly depend on power. Therefore, it does not always make sense to chase the maximum performance.

In addition, the choice of motor for maximum power also depends on the characteristics of the craft on which it is planned to be used. It is not worth exceeding the recommended power stated in the specifications — firstly, the boat transom may not be designed for a heavy large-sized unit, and secondly, the boat itself may not be suitable for acceleration to high speeds. There are also more specific recommendations. For example, from the point of view of efficiency and safety, the engine power at the level of 60 – 80% of the ma...ximum specified in the characteristics of the boat is considered optimal. Lower values may be useful if economy and low noise level are important to you, and higher values if high speed and acceleration dynamics are key points.

There is one more specific point associated with this parameter: most often, the characteristics indicate the power output directly to the propeller, however, some manufacturers (mostly east european) can go for a little trick, indicating the power on the main motor shaft. When power is transferred to the screw, losses inevitably occur, so the useful power of the motor in such a case will be less than claimed. Thus, when choosing and comparing, it's ok to clarify what kind of power is meant in the characteristics — on the propeller or on the shaft.

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 number of cylinders in a gasoline outboard engine (see "Engine type").

Usually, the optimal number of cylinders is selected by the manufacturer based on the working volume (see below) and the overall layout of the motor. Therefore, from a practical point of view, this parameter can be called secondary. At the same time, it can be a good indicator of the overall level of the engine: basic models have one cylinder, while top models can have 4 or more.

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.

The type of cooling system provided in the design of the motor.

— Air. Cooling effected by contact of air with heating parts of the engine. Air cooling systems are extremely simple, they do not require the construction of complex circuits through which liquid must circulate — a fan is enough (and some models even get by with passive radiators — characteristic ribbed protrusions on heating parts). Another advantage is the ability to work effectively regardless of the presence of impurities in the water, which allows such engines to be used quite effectively in polluted and overgrown water bodies. On the other hand, the efficiency of such cooling is low, and it is suitable only for low power units — up to 15 hp. Also note that this option is usually indicated for electric motors (see "Motor type"): although the electric motor in them is often under water and cooled by water, not air, the key point in this case is the absence of a special cooling circuit in the design.

— Water. Cooling, carried out, in accordance with the name, with the help of water. Note that we are not talking about liquid, but specifically about water cooling: the water necessary for the operation of such systems does not circulate in a vicious circle, but is taken overboard and discharged there after passing through the circuit. This is the main difference between boat cooling systems and "land" ones. If we compare this type of cooling with air, then...water systems are more complicated and expensive, but much more efficient and suitable for motors of almost any power. Note that in inexpensive low-power units, water is supplied by gravity, due to the pressure created by the screw, and in more advanced models a special pump is used.

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.