All models should be “propped” to be in the upper half of the maximum RPM
range with the boat lightly loaded and the outboard trimmed up to maximum. This
configuration allows the engine to operate within the recommended RPM range
with a heavy load.
If fuel consumption is higher than normal or the handling characteristics have
changed, the propeller may be damaged. A damaged or unbalanced propeller can
cause excessive vibration or increased noise. If you notice either condition, stop the
engine and check the propeller for nicks, cracks, pitting, distortion, or other dam-
age.
Note:
Never run with a damaged propeller. You can damage the engine or drive
unit. Keep a spare propeller on board. You can
continue your excursion without spoiling your day.
If the propeller is damaged, change it. Detailed procedures are in the engine manu-
al. Otherwise, return to port slowly to prevent further drive and engine damage
from an out-of-balance condition. Watch the temperature gauge to make sure the
engine does not overheat.
Cavitation
Cavitation is the formation of air bubbles along the surface of the propeller. Typical
causes of cavitation are a damaged propeller, the outboard trimmed out too far, or a
hull projection in front of the engine. Recondition or replace damaged propellers.
Ventilation
Ventilation is the formation of a void around the propeller, usually on entering or
leaving a sharp turn (Figure 6-2). Without water to turn in, the propeller runs free
and the boat nearly stops moving forward until the propeller finds water to turn in
again. When ventilation occurs, throttle back immediately. If ventilation continues
when you resume speed, you may have to adjust engine trim or the load.
6.3
FIGURE 6-1 PROPELLER VENTILATION
B
O
A
T
S
Y
ST
E
M
S
&
E
Q
U
IP
T
M
E
N
T
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7/9/10 1:51 PM
https://www.boat-manuals.com/
