New York Safe Boating - 2020 - 9

Inflatable Boats are lightweight collapsible boats with
inflatable sides and bow. Some may have a rigid bottom
and are powered either by oars or a small outboard motor.
Inflatable boats are
designed to be folded
and packed into in a
small compact container,
for ease of storage.
Inflatables come in many
designs from the standard
U shape to kayaks, canoes and even pontoon platforms. An
inflatable boat is a good option for people who live in an
apartment and have no place to store a regular boat.

Traditionally, outboard motors have been two-stroke
engines. Two-stroke engines are simpler and lighter than
four-stroke engines, and they produce about twice as much
power. Four-stroke engines are extremely quiet and fuel
efficient, and are rapidly gaining in popularity despite a
slightly higher cost.
Two-stroke engines often have a simple lubrication system
in which a special two-stroke oil is mixed with the fuel.
Depending on the design of the engine system, the oil can
be mixed with the fuel manually each time fuel is added, or
an oil pump can automatically mix fuel and oil from separate
tanks. Oil leaks through the exhaust port each time a new
charge of air/fuel is loaded into the combustion chamber,
so oil pollution is generally greater with two-stroke engines.
Newer designs are reducing the amount of oil getting into
the environment.

Propulsion Engines
Outboard Engines

Stern Drive Engines

The standard outboard engine is a complete propulsion unit.
Boats that use outboard engines don't have rudders, so the
boat turns in response to operator's turning of the outboard
engine. Most outboard
engines are mounted on
the transom of the boat.

Stern drive engines are also referred to as inboard-outboard
(I-O) engines. The engine portion is inside the boat, while
the drive unit is mounted on the transom. The drive unit
turns and steers
the boat, while
the engine itself
remains stationary.
Boats with these
engines don't have
rudders.

The outboard engine
has many advantages.
In general, outboards
have an excellent power
to weight ratio-so the
operator can get a lot of
power and speed out of
a small engine. These
engines are easy to service and replace. They don't take
up space in the boat, leaving more room for passengers
and gear. On the downside, they are not as efficient or
economical to operate as other types of engines.

Stern drive engines
are generally more
efficient, quieter
and longer lasting
than outboard
engines. One disadvantage of stern drive engines is that
they take up space in the boat. More importantly, there is
a risk of explosion because vapors may gather around the
enclosed engine.

Outboards come in many different designs, and may use
gas, diesel fuel or electric power. Gas engines can produce
a lot of power compared to diesel or electric engines. Diesel
engines burn less fuel and are more economical to run.
Electric power is useful for trolling motors or for people who
want a quiet ride.

Inboard Engines
Inboard engines and transmissions are mounted entirely
within the boat, with only the shaft going through the bottom
of the hull. They don't have a complicated lower unit, like
the stern drive engines do. Inboards require a rudder for
steering the boat. Since the shaft and propeller extend
below the hull, these boats usually have a greater draft,
and so may be more likely to ground in shallow water.
These types of boats also require more skill to maneuver
in reverse than
boats equipped
with outboard
or stern drive
motors. They
commonly have
an engine cover
that may take
up considerable
deck space.

There are four processes a combustion engine must
complete to propel a boat:

1)
2)
3)
4)

1) intake of the fuel,
2) compression of the fuel,
3) transform the fuel into power, and
4) release the exhaust (the waste products of the
transformation).

Movement of pistons in the engines drive these four
processes, and engines may be either two-stroke or fourstoke engines-meaning that the pistons must complete
either two or four strokes to complete the four necessary
processes.
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New York Safe Boating - 2020

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