How Outboard Motors Work
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Starting
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Outboard motors use the basic two-stroke or four-stroke motor design for combustion. With basic outboard motors, the boat begins the neutral position with the throttle in the "start" position. The vent box on the motor is opened to allow air into the combustion chamber. The motor is primed with fuel by pushing the small pump bulb. On a traditional starter, the cable is pulled. On an electric start motor, the start button is pressed. This causes the spark plugs to fire inside the motor's combustion chamber, which ignites the fuel and air mixture.
Propulsion
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The combustion action inside the outboard motor causes the pistons to move up and down. The pistons turn a round crankshaft, which is attached to a drive shaft. The drive shaft extends vertically into the water. Although the driveshaft is rotating in a vertical motion, it is attached to a gearbox via several sets of metal teeth. The gearbox is what causes the main propeller to rotate in a horizontal motion. As the propeller spins, it pushes away the surrounding water at a certain speed, usually defined by revolutions per minute (RPMs) and horsepower. For example, the Verado 6 cylinder motor's range is 200 to 300 horsepower with a maximum propeller RPM between 5,800 and 6,400.
Steering
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Steering with an outboard motor depends on the type of boat. If the boat has a steering wheel, there is usually additional linkage that connects the wheel to the outboard motor. In this case, if the wheel is turned clockwise, the motor will move the propeller to the right, causing the boat to go right. The exact opposite happens if the wheel is turned to the left. A throttle connection determines the speed of the motor.
If there is no steering wheel, the outboard motor is controlled via a large handle in the same manner. For additional braking, the driver tilts the handle down slightly, which raises the propeller up. The upward angle reduces the amount of forward thrust the outboard motor can produce, therefore slowing the boat down.
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