Comparison Mercury 9.9M vs Mercury 15M

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.

Possibility to use a petrol engine generator(see "Engine type") to power an external load.

The generator is an indispensable element in the design of any petrol engine — it is responsible for creating the spark necessary for ignition. However, not every outboard motor has the ability to power an external load from this generator — therefore, if such an opportunity is important to you, you should choose a model where it is directly stated. And the generator system can come in handy, first of all, if you plan to use additional equipment on the boat — power from the generator is in a number of ways more convenient than from autonomous batteries, and it is for it that many navigation systems, echolocation, radio communications and other instruments and equipment are made . In addition, if necessary, devices outside the boat can also be powered from the generator — for example, a starting charger for a car.

The supply voltage supplied by the generator system installed in the outboard motor.

Almost all such systems work with a voltage of 12 V — this is a standard widely used in modern automotive and water technology, it is under it that the electrical systems of the engines themselves, and electronic devices for cars and boats are made. There are practically no exceptions to this rule.

The highest current that the generator system installed in the outboard engine is capable of delivering (see above). The characteristics of the load that can be connected to the generator depend on this indicator: its total current consumption should not be higher than the maximum current of the generator, otherwise the latter will work with overload, which is fraught with malfunctions and even accidents. Also, this information is useful if you plan to use the generator to charge batteries (car or boat): each battery has its own charging current, and the power source must match them.

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 starting method provided for in the design of a gasoline outboard motor (see "Engine type"). In any such engine, the shaft must be rotated to start; this crank provides the supply of the first portion of fuel and a spark of ignition, after which the engine continues to work independently. Starting systems differ based on the manner in which said cranking is carried out.

— Manual. As the name implies, the initial impulse in such systems is provided by the operator himself manually. The most popular option is a “starter” with a rope, a jerk for which turns the engine shaft; but other launch methods may be envisaged. Anyway, manual start is convenient primarily due to the absence of a battery and a starter. This, firstly, has a positive effect on weight and dimensions, and secondly, it gives a guarantee against unpleasant situations when a dead battery does not allow the engine to be started. On the other hand, the procedure itself may require significant muscular effort, and even having experience with such systems does not guarantee start from the first jerk. Manual "starters" are typical for low-power motors, which are relatively easy to crank.

— Electric. With this method of starting, the necessary impulse is provided by a starter — a special electric motor powered by a battery. The main advantage of electric "starters" in comparison with manual ones is convenience — there is no need to scroll the engine manually,...just turn the key or press the button. On the other hand, such systems are more complex, take up more space and are noticeably more expensive. In addition, during the operation of the motor, you have, among other things, to monitor the condition of the battery — if it sits down, starting the motor will become impossible. And you will either have to change / charge the battery, or look for an external source of energy like a starter boats, having such equipment in the vicinity can be a serious problem). Therefore, a purely electric type of start is found in powerful motors (from 100 hp), for which the manual procedure is practically not applicable.

— Manual/electric. Models that combine both of the methods described above. Usually, such motors are equipped with their own starters and are regularly started electrically, and the manual “starter” plays the role of insurance in case of failures in the main system. Such systems combine the advantages of both options, but they are quite rare. This is not only due to the high price, but also because the combined starting method is suitable for a rather specific category of outboard motors: large enough to accommodate a starter with a battery, and at the same time not so heavy as to create problems during manual starting. . Therefore, this option is rare, mainly in models for 20 – 40 hp.

The presence of the motor rev limiter.

This function is most often implemented in the form of an automatic system that prevents overloads and overheating of the engine: when the temperature rises critically, fraught with overheating, the automation reduces the engine speed, allowing it to cool down (or at least not heat up further). Of course, when the system is triggered, the speed of movement decreases, but this can hardly be considered a serious nuisance compared to a motor breakdown.