Comparison Fisher 46 vs Haswing Osapian 45

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 highest current drawn by an electric outboard motor (see Motor Type). This parameter is necessary for the successful selection of the battery from which it is planned to power the motor: any battery has limitations on the maximum discharge current, and overloading (exceeding this current) is fraught with various troubles — from battery deterioration to fire or even explosion.

In addition, power consumption allows you to estimate the operating time of the motor from a particular battery. For example, if a suitable battery has a capacity of 60 Ah and the maximum motor current draw is 30 A, then at least 60/30 = 2 hours of operation from a fully charged battery can be expected.

The greatest traction force developed by the outboard motor. It is measured in kilograms: for example, indicators of 15 kg mean that the motor at maximum power pushes the boat forward with the same force with which a load of 15 kg presses on the surface below it. The recommended weight of the boat depends on this parameter (see below): the greater the weight, the “stronger” the motor must be in order to successfully move the boat through the water. The difference between deadlift and recommended weight may seem huge at first glance: for example, the mentioned 15 kg corresponds approximately to the recommended weight of 800 kg. However, this is not unusual, because the friction on the surface of the water is extremely small, and it does not take much effort to move the boat.

For a number of reasons, this indicator is indicated only for electric motors (see "Motor type").

The recommended weight of the boat on which the motor is planned to be installed. In this case, the total weight of the vessel is meant, taking into account both the hull itself and various equipment, as well as luggage and passengers. Note that this indicator is just a recommendation, and not a strict prescription — usually, the motor works quite acceptable on both lighter and heavier vessels. However, it is believed that it is when the weight of the boat matches the recommended indicators that the engine turns out to be the most efficient and safe; with less weight, you often have to “hold back” the power of the engine somewhat, and with more, the vessel can move more slowly than we would like.

As with the maximum thrust described above, the recommended weight is usually indicated only for electric motors (see "Motor type").

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.

The height of the transom of the boat for which the motor is designed. This parameter is also called “leg length” (meaning, of course, the “leg” of the motor itself, and not the boat).

The transom is a part in the stern of the vessel, designed to mount the motor. The length of the motor leg must match the dimensions of the transom, otherwise the propeller will be at an off-design depth, which is fraught with problems in operation and loss of power (regardless of whether it is too deep or too shallow). The height of the transom, usually, is indicated in the documents for the boat itself — it is from these data that one should proceed when choosing a motor according to the length of the leg.

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.