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C. Prop Slip
When traveling through water a propeller is unable to
get a complete bite because of the fluidity of water.
"Prop slip" is usually expressed as a per cent of the
computed theoretical speed. Twenty -five to thirty-five
percent prop slip is com mon for a cruiser-type boat
operating at cruising speed.
Changing either diameter or pitch will have an effect
on engine speed and prop slip, and in turn, directly
effect the performance of a boat. The propellers
included with each Four Winns
general performance based on data obtained from
on-the-water testing of that model. Variations in load,
operating conditions, environment, the individual
engine and hull perfor mance may necessitate the
purchase and use of another propeller(s).
Under your normal load conditions, the engines
should turn within the maximum RPM range when at
full throttle. If the engines exceed the recom mended
RPM, an increase in pitch or diameter is required.
If the engine RPM is too low, a de crease in pitch or
diameter is required.
The load carried in a boat will directly affect perfor-
mance of the engine. If an engine that is not develop-
ing full power, be sure the engine is properly tuned
and load conditions are those normally experienced,
before changing propellers.
For shipping reasons, the propellers are not factory
installed. Initial installation of the propel lers will be
performed by the dealer during pre-delivery ser vice.
Consult your specific engine manufacturer's owner's
manual for propeller installation instructions.
See Figure E4.
Straight Forward Position
Front Propeller
Rear Propeller
Figure E4: Counter-Rotating Propellers
Engines, Drives and Instrumentation - Section E
boat provide the best
®
NOTICE
Should it be necessary to change propel lers,
always use an appro priate propeller removal
tool or "Prop Puller." DO NOT attempt removal
using a ham mer. Dam age to the propeller or
propeller shaft can result.
Be sure the propellers are of the correct blade con-
figuration, diame ter, pitch, and shaft size to assure
good performance. For additional information on
factors affecting performance and/or assistance with
your selection, please consult your Four Winns dealer.
E - 5
COOLING SYSTEMS
A. Fresh Water Cooling System
The fresh water system is the engines' internal cooling
system. The freshwater cooling system ensures the
engine operates at the correct temperature. It is a
"closed water cooling" system and must be filled with
a mixture of at least 40% concentrated coolant and
60% water to protect against internal corrosion,
cavitation and damage caused by freezing. This
system provides adequate engine cooling without
exposing the internal engine to the detrimental effects
of surface water, including salt, highly polluted or silt-
laden water. The engine owners manual provides
addi tional infor mation regarding service and mainte-
nance of this equipment. See your Four Winns dealer
for availability.
Should an en gine in take or an ex ha ust or
cool ing hose rup ture, turn the en gine off and
close the seacock immediately. Proceed under
tow, if neces sary, to a service facility for
appropriate repairs; maintain a close visual
watch on the prob lem hose and also on the
bilge water level.
B. Seawater Cooling System
The seawater system is the boat's external cooling
system. Surface water is used a cooling medium for
the control system oil cooler, fuel cooler, intercooler,
engine oil cooler and heat exchanger. The cooling
water employed enters the system through a water
intake on the drive-unit and is relinquished through the
exhaust pipe elbow where it is mixed with the exhaust
gases. Some boating areas require that additional
Owner's Manual Page 56
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