1. Transducer cables should be run separately, not bundled together with other wiring or run close to the engine. This can cause noise-generated marks on the fish finder. (Read: Understanding Transducers.)
2. Power-line filters such as Newmar’s ( 714-751-0488 email@example.com ) PC-10 and PC-25 can silence noise when connected to an instrument’s 12-volt power cables. Install the filter close to the offending equipment.
3. Those snap-on “ferrite core RF chokes” that are commonly used on computer cables to minimize RF interference (available at Radio Shack and electronic parts stores) also reduce noise on electronics cables.
4. In extreme cases, you can often screen out noise being picked up on equipment wiring like a stereo set by substituting the affected wires or cables with shielded wiring.
5. Sometimes just twisting the wires together along their entire length can suppress noise intrusion (you can also purchase pre-twisted cable).
6. Connecting a wire from an instrument’s metal case or grounding stud to your boat’s ground can squelch electrical noise.
7. A 0.01-microfarad capacitor connected across the two leads of a radio’s or stereo’s speaker will often eliminate noise caused when transmitting on a radio. This also works for gauges that experience fluctuation when talking on a radio.