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slip is common for a cruiser-type boat operating at cruis-
ing speed.
Therefore the deduction can be made that a propeller, of a
certain diameter, with a 10 inch pitch, rotating at 3600
revolutions per minute, with a prop slip of 30%, would move
the boat at a rate of 24 miles per hour.
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 propeller(s) 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,
environment, the individual engine and hull performance
may necessitate the purchase and use of another
propeller(s).
Under your normal load conditions, the engine(s) should
turn within the maximum RPM range when at full throttle.
If the engine(s) exceeds the recommended RPM, an in-
crease 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.
B - 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 B3.
Vista Owners Manual
10/93
The running angle can be controlled through the use of
power trim and trim tabs. See Section B-6 Trim Tabs,
for information on the use of trim tabs.
Figure B3: 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 Own-
ers manual.
Section B
Page 5
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