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Propulsion System
DO NOT PAINT THE OUTBOARD MOTOR WITH ANTIFOULING
PAINTS DESIGNED FOR BOAT HULLS. MANY OF THESE
PAINTS CAN CAUSE SEVERE DAMAGE TO THE ENGINE.
CONTACT YOUR DEALER OR ENGINE MANUFACTURER FOR
INFORMATION ON THE PROPER PAINTING PROCEDURES.
3.3 Engine Lubrication
4-cycle outboard engines incorporate a pressure-
type lubrication system with an oil sump in the
crankcase that must be kept full of the type and
grade of oil recommended by the engine manu-
facturer. It is normal for 4-cycle engines to con-
sume a small amount of oil. Therefore, the oil
must be checked before each use and changed
at regular intervals as instructed by the engine
owner’s manual.
Notice:
Always monitor the oil level in the crankcase
andonlyusethetypeofoilspeciedbythe
engine manufacturer.
3.4 Engine Cooling System
Outboard engines are raw water (seawater)
cooled. Water is pumped through the water in-
lets, circulated through the engine block, and
relinquished with the exhaust gases through the
propeller hub. The water pump uses a small im-
peller made of synthetic rubber. The impeller and
water pump cannot run dry for more than a few
seconds. In most outboard motors, some cooling
water is diverted through ports below the engine
cowling. This allows the operator to visually check
the operation of the cooling system. When the en-
gine is started, always check for a steady stream
of water coming out of those ports.
Notice:
If the boat is used in salt or badly polluted
water, the engine should be ushed after
each use. Refer to the engine owner’s man-
ualfortheproperengineushingprocedure.
NEVER RUN AN OUTBOARD MOTOR WITHOUT WATER
FLOWING TO THE WATER PUMP. SERIOUS DAMAGE TO
THE WATER PUMP IMPELLER OR ENGINE COULD RESULT.
3.5 Propellers
Propellers convert the engine’s power into thrust.
They come in a variety of styles, diameters and
pitches. The one that will best suit the needs of
your boat will depend somewhat on your applica-
tion and expected average load. Propeller sizes
are identied by two numbers stamped on the
prop in sequence. The 1st number in the sequence
(example 14” x 21”) is the diameter of the propel-
ler and the 2nd number is the pitch. Pitch is the
theoretical distance traveled by the propeller in
each revolution.
Always repair or replace a propeller immediately
if it has been damaged. A damaged and therefore
out of balance propeller can cause vibration that
can be felt in the boat and could damage the en-
gine gear assembly. Refer to the engine owner’s
manual for information on propeller removal and
installation.
3.6 Performance Issues & Propellers
It is extremely important that the boat is propped
to run at or very near the recommended top RPM
with an average load. If the top RPM is above or
below the recommend range, the propeller must
be changed to prevent loss of performance and
possible engine damage.
Notice:
Before changing a propeller to correct boat
performance problems, be sure other factors
such as engine tuning, bottom and running
gear growth, etc. are not the source of per-
formance changes. Always be sure the load
conditions are those normally experienced,
before changing the propeller.
Your boat was shipped with a propeller that typi-
cally provides optimum performance for your boat.
However there are factors that can aect perfor-
mance and propeller requirements.
Some are as follows:
• You should be sure the load conditions are
those normally experienced. If the boat ran
in the required RPM range when it was new
and you have not added any additional gear or
heavy equipment and have not damaged the
propeller, there is a good chance the propeller
is not the problem.
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