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Know your boat motors before buying

Written By : SUN FIJI ADVERTISING. Choosing the right type of propulsion system for your boat is a very important matter. Its weight and horsepower will both have an impact
11 Oct 2010 12:00

Written By : SUN FIJI ADVERTISING. Choosing the right
type of
propulsion
system for your boat is a
very important matter. Its
weight and horsepower will
both have an impact on the
performance of your
vessel. If your vessel is
underpowered, its engine
will work hard continually
and will provide poor
performance. Additionally
if your vessel is
overpowered, it may exceed
the safe operating speed
that was designed for the
vessel.
The definition of an
outboard motor is a
detachable engine
mounted on outboard
brackets on the stern of
your boat. Today’s
outboard motors range in
horsepower from 1.0 HP to
over 300 HP per engine.
Outboard motors can be
used in all types of waters.
There are two general
types of outboard motors;
2-Stroke and 4-Stroke
motors.
2-Stroke Benefits
m Generally better
acceleration out of the
hole and at top end
m Overall, excellent
power to weight ratio
m Basic models are
simple by design
m Generally lower
priced than a 4-stroke
(carburated 2-Stroke only)
m No need to change
the oil
m Generally weighs
less than a 4-stroke
m Usually better
fuel efficiency than
carburated 2-Strokes
(comparable to 4-Stroke)
m Usually quieter
than carburated 2-Stroke
(comparable to 4-Stroke)
One noticeable
difference between 2 stroke
and 4 stroke engines is
weight of a similar horse
powered engines. 4-strokes
tend to be heavier than a 2-
stroke engine of
comparable horse power. 2-
Stroke engines uses a gas
and oil mixture, while a 4-
stroke burns gasoline. A 4-
stroke engine is more like
a car engine including an
oil filter and generally has
lower torque than 2-
strokes.
4-Stroke Benefits
m Low emissions
m Strong top end
and good acceleration
m Excellent fuel
economy
m Quiet operation
m Engine
management systems
m Electronic
ignition systems
m The oil is added to
the engine rather than the
fuel allowing for clean and
efficient fuel consumption
Diesel engines rely on
compression to power the
engine. Compared to a
traditional gas engine, the
engines are similar by
design, as they have
crankshafts and cylinders
and pistons; however, the
fuel systems are
completely different and
more complex on a diesel
engine.
Diesel engines range in
size and horse power.
Diesel engines are widely
used in other parts of the
world, while in the United
States, they are typically
found in boats larger than
35 feet. The main reason
that diesel engines are not
used in smaller boats is
weight. The engine in
general weighs more than a
gas engine. However, they
are used in larger vessels
because of their ability to
produce torque.
In general diesel
engines run at lower RPM’s
than a traditional gas
engines.
Benefits / Notes
m No carbon
monoxide to worry about
in cabins or on the back of
boats
m Excellent torque
m Long life
expectancy
m Low running costs
m Majority of the
engines weigh more than a
traditional gas engine
m Non-Explosive
fuel
While similar to what is
under the hood of your car,
gas engines used in marine
applications are modified
to make them marine
engines. Gasoline inboard
engines range in
horsepower from 90 HP to
over 1000 HP per engine and
are used in a variety of
engines from tow sport
boats to large cruisers.
In an inboard engine
configuration, the engine
sits amidships, with a drive
running through the
bottom of the boat to a
propeller, with a separate
rudder used for steering. A
transmission is often used
to transfer power from the
engine to the propeller.
Exhaust is passed through
the stern of the boat.
Inboards are also common
for tow sports such as
waterskiing, wakeboarding
as they allow the propeller
to be brought forward of
the back of the boat,
providing area for
platforms to assist skiers
in entering and exiting the
boat.
Benefits/Notes
m Simple drive
system can lower
maintenance
m No means to trim
propeller
m Low running costs
m Quite and out of
the way
These propulsion
systems have the
advantage of having no
propeller to cause
potential danger to people
in the water and marine
life. They are usually
inboard engines that take
in water that flows through
a pump powered by an
impeller. The water is then
discharged at high pressure
through a nozzle that
propels the boat forward.
The nozzle swivels to
provide steering to the
boat. Most personal
watercraft use jet drives.
Note: When power is not
being applied, a jet driven
vessel loses its steering
because it is the stream of
water that steers the boat.
Keep hands, feet and hair
away from the pump intake
and do not operate in
shallow water.
Source:
www.discoverboating



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