P
E R F O R M A N C E
4–1
C h a p t e r 4 : P e r f o r m a n c e
P
ERFORMANCE
F
ACTORS
Maximum performance is dependent on many factors and cannot be guaranteed. These factors
will vary with changing conditions. Some of these factors are listed below. Reference the trouble
shooting guide, page 65 in
Sportfish, Cruisers, Yachts Owner’s Manual,
for additional suggestions
on adjusting performance.
Engine Efficiency
Engines operate most efficiently at the RPM confirmed in the engine operating manuals,
assuming your boat is equipped with the correct engine(s), the engine(s) are properly tuned,
and the drive system(s) are in good condition. Efficiency will decrease if normal care and
maintenance is not performed. Neglecting the engines will cause power to drop and speed to
decrease. In addition, expensive repairs may become necessary. Be sure to follow all
instructions in the engine operation manual(s).
Weather Conditions
Weather conditions affect engine performance. Barometric pressure and humidity both
influence horsepower. A change of weather could cause a 10% loss in horse power on some
hot days.
Load Distribution
A decrease in performance will be noted when gear, equipment, passengers, and fuel are
added. This type of extra load will affect the performance of the boat according to the
distribution of the weight. Water accumulation in the bilge, another type of extra load, will
affect performance. Keep the bilge dry to eliminate this problem.
Marine Growth
Maximum performance is obtained only when your hull bottom is clean. Marine growth on
the bottom of the boat will increase resistance and decrease speed. These conditions will also
increase fuel consumption. Reference
“Cleaning” on page 6–1
for more information on
cleaning your hull bottom.
Trim
Most outboard models are equipped with power tilt and trim mechanisms. The purpose of
power tilt is to raise the engine for launching, loading, or trailering your boat. Power trim may
be used to adjust the boats planing performance and running attitude. See Power trim in
Sportfish, Cruisers, Yachts Owner’s Manual
on pages 52 and 72.
Trim refers both to the weight distributions inside the boat and to the angle of thrust of the
drive unit. The angle of thrust of the drive unit forces the bow up or down. The trim tabs on
your boat also control the trim of the boat, similar to the power trim. Refer to the Trim Tabs
section in Chapter 8 for additional information.
