There are positive and negative aspects concerning the different small outboard motor styles that should be considered when planning a motor purchase. Whether it be a two- or four-stroke motor design, and a water- or air-cooled small outboard, the selected motor's style should compliment the boat it is going to power. Other integral factors to consider include the boat's style of transom, the mounting location on the intended craft's transom, and the option of a long or short shaft.
Through the years, two-stroke outboard boat motors have powered nearly every type of small boat manufactured around the world. The exhaust smell of a two-stroke small outboard motor is easily recognized by many boaters and fishermen. The thick, smoky emissions produced from mixing the gasoline with the two-stroke motor oil creates a scent that is memorable. In an increasingly green environment, however, that smoke is also an unwelcome signal of air pollution. It is this reason above all others that the four-stroke small outboard boat motor is becoming increasingly popular and more commonly found on many boats.
The four-stroke outboard motor eliminates the need for pre-mixing the fuel and oil. This motor design operates the same way as the family sedan by using plain unleaded gasoline in the fuel tank and motor oil in the small outboard motor's engine case. The four-stroke motor produces no smoky exhaust and, in most instances, operates with a reduced noise emission as well. The quieter operation is credited by many to offer an increasingly relaxing day on the water as compared to the two-stoke motor.
Many two-stroke motor designs are also air-cooled. This feature eliminates costly water pump repair that so often plagues small outboard motor owners. By eliminating the water pump, the engine is able to operate in very shallow water, occasionally running with only half of the propeller dipping into the water. This feature is popular with sportsmen who use boats to venture into shallow water in search of game birds to hunt. By being able to run the propeller so shallow, contact with rocks and stumps is eliminated.
Shaft length is perhaps the most critical component of a small outboard. When used as an emergency motor or as a trolling motor alongside a larger outboard, the smaller motor is often mounted high on a kicker bracket. This requires the small motor to have a long shaft so that it can reach the water.