| Outboard motors for a boat are developed
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| | outweigh the range deficiencies shared
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| as a self-contained unit with engine,
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| | with electric cars. Diesel outboards are
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| subsidiary systems, and propeller,
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| | also available, but their weight and cost
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| designed to be mounted at the stern
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| | makes them impractical for most purposes.
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| (rear) of the craft. They are the most
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| | A few outboard motors have been produced
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| common method of propelling small
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| | with pump-jet propulsion replacing the
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| watercraft.
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| | conventional propeller. Like other types
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| As well as providing propulsion,
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| | of pump-jet propulsion systems, they
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| outboards provide steering control, as
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| | offer virtually no cavitation, making the
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| they are designed to pivot over their
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| | boat more manoeverable, and can operate
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| mountings and thus control the
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| | in very shallow water. However, the low
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| orientation of the propeller. The
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| | efficiency compared to propellers has
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| transmission leg in the water also acts
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| | seen them restricted to specialised
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| as a rudder even when the propeller is
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| | applications.
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| not providing power.
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| | History and developments
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| When boats are out of service or being
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| | The first practical outboard motor was
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| drawn through shallow waters, outboard
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| | created by Norwegian-American inventor
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| motors can also be tipped forward over
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| | Ole Evinrude in 1909.
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| their mounts to elevate the propeller and
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| | Historically, most outboards have used
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| transmission shaft out of the water to
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| | two-stroke cycle engines due to their
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| avoid accumulation of seaweed or hitting
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| | simplicity (and consequent reliability),
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| underwater hazards such as rocks.
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| | low cost, and high power-to-weight ratios
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| Types of motors
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| | - weight issues being particularly
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| Small outboard motors are truly
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| | important as too much weight over the
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| self-contained, with integral fuel tanks
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| | stern of boats tends to impede their
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| and controls mounted on the body of the
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| | handling. However, the high emissions,
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| motor and steered by a "tiller" directly
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| | and thus both environmental concerns and
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| connected to the motor. Such small motors
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| | the cost of technology to meet emissions
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| can weigh as little as 12 kilograms
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| | standards, has led to the gradual gain in
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| (approximately 26 pounds) and provide
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| | popularity of four-stroke cycle
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| sufficient power to move a small dinghy
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| | outboards, particularly for lower-end
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| at around 15 km/h (9 mph), far faster
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| | machines. High-end outboards have tended
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| than possible with oars. They are highly
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| | to remain two-stroke designs, as the fuel
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| portable, able to be removed by simply
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| | injection technology required to meet the
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| loosening their mounting clamps. Small
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| | emissions standards and fuel economy
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| outboards usually use a manual pull start
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| | targets costs proportionally less for
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| ignition system while larger models often
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| | these motors and weight issues are more
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| have electric start similar to a car.
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| | important.
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| Manufacturers have produced large
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| | Marine engines also benefit from their
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| outboard designs, with sufficient power
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| | proximity to an endless supply of cold
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| to be used on boats as long as 9 metres
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| | water by using it once for cooling and
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| (30 feet) or more. Manufacturers have
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| | then ejecting the now-heated water. This
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| also produced electric outboards. These
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| | allows marine engines to avoid the cost
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| are used for specialised applications,
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| | and weight of radiators and cooling fans
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| notably trolling for bass in the US,
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| | normally associated with land-based
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| where their quietness and zero emissions
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| | engines.
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