Four winns Vista 328 Owner's Manual page 44

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 percent of the computed theo-
retical speed. Twenty-five to thirty-five percent prop slip is
common 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® boat provide 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 performance may ne-
cessitate 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 recommended RPM, an increase
in pitch or diameter is required. If the engine RPM is too
low, a decrease in pitch or diameter is required.
An engine that is not developing full power and the load
carried in a boat will directly affect performance of the
engine. Always be sure the engine is properly tuned and
load conditions are those normally experienced, before
changing propellers.
NOTICE
For twin engine installations, always check drive
shaft rotation before propeller installation. A right
hand rotation propeller must be installed on the
stern drive to the starboard engine. Similarly, a
left hand prop must be installed on the port stern
drive.
For additional information on factors affecting performance,
please consult your Four Winns dealer.
E - 6 RUNNING ANGLE & POWER TRIM/TILT
Hull planing surfaces have the least amount of drag at a
three to five degree angle with the water. This is the pre-
ferred running angle when boating. The running angle has
a significant impact on top speed and handling. Heavy
load or certain water conditions may make it difficult to
achieve the optimum running angle. See Figure E3.
The running angle can be controlled through the use of
power trim and trim tabs. See Section E-7 Trim Tabs, for
information on the use of trim tabs.
298/328 Vista Owner’s Manual
09/00
Figure E3: Running Angle
A. Power Trim
Trim angle is how far in or out, the lower unit is posi-
tioned in relation to the bottom of the boat. The trim
angle of the lower unit has a distinct affect on the running
angle of the boat.
The power trim system permits control of the trim angle
of the drive unit relative to the boat, at the touch of a
button.
It allows the drive unit to be raised (trimmed out) for shal-
low water operation. Power trim also allows the operator
to adjust the drive unit while underway to provide the
ideal running angle for a given load and water condition.
Additional information can be found in the Engine Owner's
manual.
3 TO 5
0 0
Section E
Page 4