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 | 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 |
The boat’s engine | 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. |
Cavitation from the boat’s propeller | 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 transducerat all times. |
Troubleshooting | 138 |