Blackfin 272CC - 3.5 Propellers; 3.6 Performance Issues & Propellers

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Propulsion System
CAUTION
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
andonlyusethetypeofoilspeciedbythe
engine manufacturer.
3.4 Engine Cooling System
Outboard engines are raw water (seawater)
cooled. Water is pumped through the water
inlets, circulated through the engine block, and
relinquished with the exhaust gases through the
propeller hub. The water pump uses a small
impeller 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 visu-
ally check the operation of the cooling system.
When the engine 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enginesshould be ushed after
each use. Refer to the engine owner’s man-
ualfortheproperengineushingprocedure.
CAUTION
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
The propellers convert the engine’s power into
thrust. They come in a variety of styles, diam-
eters and pitches. The one that will best suit the
needs of your boat will depend somewhat on your
application and expected average load. Propel-
ler sizes are identied by two numbers stamped
on the prop in sequence. The 1st number in the
sequence (example 14” x 21”) is the diameter of
the propeller, and the 2nd number is the pitch.
Pitch is the theoretical distance traveled by the
propeller in one 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 propellers must
be changed to prevent loss of performance and
possible engine damage.
Twin engine boats are equipped from the factory
with counter rotating engines that are mounted
to achieve quicker planing and optimum perfor-
mance. Therefore, the left hand rotation engine
is mounted on the port side of the transom and
the right hand rotation engine is mounted on the
starboard side. You should make sure that each
propeller matches the rotation of the engine.
Notice:
Before changing propellers to correct boat
performance problems, be sure factors such
as engine tuning, bottom and running gear
growth, etc. are not the source of perfor-
mance changes. Always be sure the load
conditions are those normally experienced,
before changing propellers.
Your boat was shipped with propellers that typi-
cally provide optimum performance for your boat.
However there are factors that can aect perfor-
mance and propeller requirements.