Outboard starters are used to crank large motors and start them easily. Made in the same manner as an automobile starter, outboard starters use a battery to energize the Bendix and engage the starter ring. While mid-sized and smaller outboard motors are equipped with both pull rope and electric outboard starters, the larger motors are equipped with the electric starters only. These outboard starters typically rely on a separate dedicated battery to provide the electricity to start them. On some outboard motor models, the outboard starters also double as electrical generators and charge the battery while the motor is running.
Outboard starters that double as generators function much like the starter motor on a common riding lawn mower. This type of starter motor has a drive gear that remains in constant contact with the starter ring and does not utilize a Bendix. As power is applied to the starter motor, it spins the engine over until it starts. Once started, the brushes and wiring inside of the starter motor become energized and take on the characteristics of an alternator or generator and send current back to the batteries charging it. Also, an onboard regulator switches the charging element within the starter on and off to prevent overcharging the boat's battery.
Many smaller outboard boat motors use an optional electric starter. This type of starter is often actuated by a small switch mounted on the equipment, such as on a tiller or snow-blower handle. In cold weather, these optional outboard starters are very helpful in cranking over the cold engines. These outboard motors are very difficult to pull start when cold and are often so hard to pull start that the recoil rope or handle actually breaks when a pull start is attempted. In contrast, the push of a button spins the outboard over with ease when an optional electric starter is installed.
It is extremely important that the battery used to power outboard starters not be wired into a trolling motor or other electrical device in an attempt to provide them with reserve power. The reason for this is that if drained, the battery cannot supply the necessary power to start the outboard motor. With the larger motors that do not have pull-start capabilities, this creates a very real danger of a boater becoming stranded. A best practice is to install an extra battery if the need arises and keep the outboard's battery use strictly for the outboard starter.