Humminbird 757c - Manual (Page 146)

137
Display Problems
There are several main conditions or sources of possible interference that may
cause problems with the quality of the information displayed on the control
head. Look in the following table for some symptoms of display problems and
possible solutions:
Problem Possible Cause
The control head loses
power at high speeds.
When the boat moves
at higher speeds, the
bottom disappears or
suddenly weakens, or
the display contains
gaps.
There are no fish
detected, even when
you know they are in
the water under the
boat, or sonar readings
seem weak or faulty.
If the power output of your boat’s engine is unregulated,
the control head may be protecting itself using its over-
voltage protection feature. Make sure the input voltage
does not exceed 20 Volts.
The transducer position may need to be adjusted. A mix
of air and water flowing around the transducer
(cavitation) may be interfering with the interpretation of
sonar data. See your Installation Guide for suggestions on
adjusting the transducer position.
Electrical noise from the boat’s engine may be interfering
with sonar reception. See Finding the Cause of Noise for
more information.
Sonar readings may be affected if the transducer is not
positioned correctly (i.e. mounted at an angle, not
straight down), or there is some kind of mechanical
interference, either because it is mounted inside a hull
that is too thick for proper sonar transmission, the bond
between the transducer and the hull is not airtight, or
because the transducer is dirty. Check with your
Installation Guide for guidance on re-positioning the
transducer, and make sure the transducer is clean.
Low battery voltage may be affecting the power of signal
transmission.
Electrical noise from the boat’s engine may be interfering
with sonar reception. See Finding the Cause of Noise for
more information.
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