Humminbird HELIX 5 DI, Operation Manual

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Troubleshooting
80
Finding the Cause of Noise
Electrical noise usually affects the display with many black dots at high speeds, and high
sensitivity readings. One or more of the following sources can cause noise or interference:
Possible Source of Noise Isolation
Other electronic devices
The boat’s engine
Cavitation from the boat’s
propeller
Turn off any nearby electronic devices to see if the
problem goes away, then turn them on one at a time to
see if the noise re-appears.
To determine whether the boat’s engine is the source of
the noise, increase the RPMs while the boat is in neutral
and stationary to see if the noise increases
proportionately; if noise appears when you rev the
engine, the problem could be the spark plugs, alternator,
or tachometer wiring. Replace the spark plugs with
resistor plugs, install an alternator filter, or route the
control head power and transducer cables away from
the engine wiring.
Turbulence created by the propeller can cause noise; make
sure the transducer is mounted at least 15” (38 cm) from
the propeller, and that the water flows smoothly over the
face of the transducer at all times.