Comparison Fisher T2,5CBMS vs Parsun T2.6CBMS

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 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.