Humminbird Matrix 67 User Manual download pdf (Page 84)

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.

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Humminbird Matrix 67 User Manual Page 84