Table of Contents
Advertisement
NEVER operate the propulsion engine while
everyone onboard is sleeping. Fatal carbon
monoxide poison ing can occur.
For additional information, refer to Section B-2 Carbon
Monoxide.
E - 3
ENGINES
Consult the Engine Owners Manual included in the
owner's packet for additional operation and mainte-
nance information.
E - 4
PROPELLERS
Knowledge of the propeller is most easily gained
through better understanding of the terminology used
to refer to the aspects of propeller size and perfor-
mance.
NOTICE
Never run with a damaged propeller. You can
damage the engine or drive unit. Keep a spare
propeller and the necessary tools to replace a
propeller onboard.
A. Diameter
Diameter is twice the distance from the center of
the prop shaft to the extreme tip of a propeller blade.
Increasing or decreasing propeller size will have a
direct bearing on the RPMs (revolutions per minute) an
engine will develop. This is due to the greater amount
of propeller blade surface in contact with the water.
See Figure E1.
B. Pitch
Pitch is a measure of helix angle, or angle of attack,
of the rotating blade. Pitch is easily under stood if one
imagines the propeller rotating through a semisolid
such as butter or jello. The distance the propeller will
travel in one revolution is called "Pitch." Increasing
or decreasing pitch will also have a direct bearing on
engine RPMs because of the greater bite taken by
the blade with each rotation. See Figure E1.
Engines and Instrumentation - Section E
Figure E1: Propeller Pitch & Diameter
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 c ent of the
computed theoretical speed. Fifteen to twenty-five
percent prop slip is com mon for a sport-type boat
operating at cruising speed.
Changing either diameter (Rx2) or pitch will have
an effect on engine speed and prop slip, and in
turn, directly affect the performance of a boat. The
propeller(s) included with each Four Winns
vides the best general performance based on data
obtained from on-the-water testing of that model.
Variations in load, operating conditions, environ-
ment, the individual engine and hull perfor mance
may necessitate the purchase and use of another
propeller(s).
Under your normal load conditions the engine should
turn within the maximum RPM range when at full
throttle. If the engine(s) exceeds the recom mended
RPM, an increase in pitch and/or diame ter is re-
quired. If the engine RPM is too low, a de crease in
pitch and/or diameter is required.
Radius
boat pro-
®
Owner's Manual Page 53
Advertisement
Table of Contents
