How do I choose a fish finder and chartplotter for my boat?

Choose the transducer and chart coverage first, then buy a display you can read comfortably from your normal steering position. For coastal fishing in 10 to 80 metres, a combined 7 to 9-inch chartplotter with conventional CHIRP sonar is a sound starting point; add side-scanning sonar to help find wrecks, reefs and seabed structure.

Check the boat and equipment

Check the hull material, engine arrangement, mounting space and labels on existing transducers and instruments. These determine what you can install and reuse. Keeping compatible equipment often saves more than buying a cheaper display.

• Outboard motorboat: a transom-mounted transducer is usually the simplest option, provided it sits in clean water clear of hull steps, strakes and propeller turbulence.
• Sailing yacht or shaft-drive motorboat: a properly positioned through-hull transducer is often preferable because the transom may lift clear or encounter disturbed water.
• Solid GRP hull: a compatible in-hull transducer can avoid drilling, but it cannot measure water temperature directly and loses some sensitivity. Ordinary shoot-through installations are unsuitable through sandwich core, aluminium or steel.

Record instrument makes, model numbers and connector types. NMEA 2000 can share supported data such as depth, position and AIS, but sonar images and radar normally need the manufacturer's compatible network. A matching plug alone does not establish transducer compatibility.

Match sonar to fishing depth

Start with conventional CHIRP. It shows depth, bottom shape and targets beneath the boat. High-frequency CHIRP generally suits shallower coastal fishing; lower frequencies become useful as depth increases. Performance depends on the transducer, installation, sea conditions and bottom type, not just the advertised maximum depth.

Down-scanning sonar gives a more detailed view of structure directly beneath the boat. Side-scanning sonar searches to port and starboard, helping locate reef edges, wrecks and shoals while moving slowly. Neither replaces reliable conventional sonar for tracking the bottom underway.

For routine fishing in 10 to 80 metres, a compatible recreational CHIRP transducer is normally sufficient. Deeper offshore fishing may justify a 600 W or 1 kW transducer and matching sounder. Check the manufacturer's recommended operating depths before specifying either.

Check the exact display variant. Some chartplotters have built-in sonar; others need an external module. For example, the 2024 Furuno TZtouchXL range included an internal dual-channel 1 kW CHIRP sounder on TZT10X, TZT13X and TZT16X models. That specification does not automatically apply to every screen in the range.

Choose the screen and charts

A 7-inch screen works on a small console, but a split view of chart and sonar leaves relatively little space for either picture. A 9-inch screen is usually easier to read while standing at the helm. Make a cardboard template to check that the display, bracket and rear cable bends fit without obscuring instruments.