An outboard motor is basically a single unit consisting of an engine, gearbox, and a propeller or jet drive, and it's used as an actuation device for boats. They are also used as auxiliary power devices for large boats whenever the need arises. Outboard motors are more convenient to use, as far as installation, maintenance, handling and repair is concerned.
Outboard motors are available in a number of sizes, according to the purpose which they serve. Their weight ranges from a few kilograms to about a few hundred kilograms. This also varies with the application that they're used for, wherein the weight increases with the number of parts and also with the kind of fuel used. A basic description of the types of motors available in the market is as follows.
The smallest outboard motors that are available are the portable kind, which are also the lightest of their kind. Their weight can be as little as 12 kilograms, and they provide about 15 hp of power. The speeds that these motors can help one achieve are close to about 15 km/hr, which may not be much, but there are applications wherein these kinds of speeds are required. These motors are hence used to power small watercraft, to provide auxiliary power to sailboats and for trolling aboard bigger boats.
Large outboards, as their name suggests, are much, much bigger in size, and also provide larger amounts of power. These contain engines with 2, 3 or cylinders, and can produce power ranging between 15 and 135 hp. These motors are used with large boats, which can be as long as 18 feet, and the hull of which may be as huge as 17 feet in length.
Motors with electric actuation are also available nowadays. These motors have an advantage over other motors, as far as quiet operation and zero emissions are concerned. These may not produce very high amounts of power, but they certainly are advantageous in areas where gasoline motors are prohibited and where silent working is required. An example would be fishing for freshwater species such as bass.
Another type of outboards uses diesel as fuel, but these have a disadvantage when it comes to the exhaust gases that they emit. These motors are also extremely heavy, which makes them a little difficult to use.
The last among this assortment of motors is the pump jet motor, which uses a jet of water for propulsion. These motors are very useful when operation in shallow water is demanded.
Coming to the criteria for selection of an outboard motor, there are two major requirements that must be fulfilled, before an outboard motor is fully qualified to perform, and the results achieved satisfy the customer. The first among these requirements is the power that is produced by the motor. There are certain standards that must be satisfied before a motor is graded as working in perfect condition. The second criterion is the shaft length of the motor, which again affects the efficiency of the boat, according to the application that it is being used for.
