Fitting navigation electronics and transducers
How to fit a chartplotter, log, echo sounder and transducers and link them over an NMEA 2000 backbone into one reliable network.
Modern navigation electronics are a network of co-operating devices: a chartplotter, a log/sounder (DST — depth, speed, temperature), a wind instrument, a compass/AIS and an autopilot. The heart of the integration today is the NMEA 2000 bus — a common, standardised backbone to which devices are connected by drop cables. Before you start drilling into the hull, plan the whole network topology and the placement of the displays. A good plan eliminates most of the later problems with cable runs and interference.
The NMEA 2000 bus has strict rules, and breaking them causes faults that are hard to diagnose. The backbone must be terminated at BOTH ends with 120 ohm terminating resistors, and devices are connected with T-pieces. The bus needs power at a single point (usually through a power injector) and has limits on the length of the drops and of the whole network. A missing terminator, power fed in twice or over-long drops are the classic reasons for data disappearing. Leave spare ports for future extensions.
The sounder transducer is most often fitted through the hull (through-hull) or inside, bonded to the laminate (in-hull). Through-hull mounting gives the best performance but needs a hole and the right orientation: the transducer must look vertically down, so on a hull with deadrise a fairing block is used to compensate for the angle. The position should be in clean, undisturbed water flow, away from the wake behind the keel and the propeller, to avoid air under the sensor disturbing the echo.
Drilling the hull for a skin fitting is a critical operation — NOTE: a mistake risks sinking the boat. Cut the hole precisely, seal the edges in the core with resin and bed the fitting on marine sealant (polyurethane or MS polymer), tightening the backing nut. Always fit an emergency bung (a wooden plug) nearby. Check for leaks after launching. A paddle-wheel speed transducer needs periodic cleaning of the fouling that jams the impeller.
Mount the displays and plotter where they are clearly visible and sheltered, with access behind for the wiring. Run the supply from the panel through a suitable fuse, using the right cross-section and keeping the voltage drop minimal. Place the GPS and AIS antennas and the masthead wind sensor away from sources of interference; run signal cables separately from heavy power cables and the engine wiring, to limit interference. The connections must be watertight or sheltered.
Once the network is connected comes configuration and calibration, and skipping it makes the data worthless. Calibrate the speed log over a known distance in both directions (to compensate for the current), set the depth offset (from the bottom of the keel or from the waterline), swing the compass and calibrate the wind sensor (correcting for the offset at the masthead). In the Raymarine, Garmin or B&G ecosystems, the configuration is done from the plotter, which sees every device on the bus and lets you assign the data sources.
Finally, run an integration test: does the autopilot get a heading, does the AIS show targets, do the wind and speed data reach every display? It is worth drawing a simple network diagram noting what is connected where and where the terminators and the power are — invaluable for future fault-finding. A carefully planned and calibrated installation runs reliably for years; most faults come from breaking the bus rules, a badly placed transducer or a skipped calibration.
Material prices — products and options
Indicative prices in EUR (incl. VAT), as of July 2026. Products widely available in Europe; prices depend on the shop, the pack size and consumption. The links lead to example shops that ship across the EU. Dollar amounts are converted at 1 EUR = 1.1622 USD (ECB, 7 September 2026) and rounded — treat them as a rough guide, not a price in a US shop. Imperial values in brackets are conversions of the metric figure.
Chartplotters / multifunction displays (MFD)
- Garmin — ECHOMAP UHD2 72cv (7″)
budget plotter with CHIRP sonar, GPS, Wi-Fi, transducer included€600–680 (≈$697–790) - Raymarine — Element S 7″
chartplotter with GPS and Wi-Fi, LightHouse Sport system€520–620 (≈$604–721) - B&G — Zeus S 9″
sailing touchscreen chartplotter with sailing modes, NMEA 2000€1500–1700 (≈$1,743–1,976) - Lowrance — HDS PRO 12″
premium 12″, Active Imaging HD sonar (transducer not included)€3200–3600 (≈$3,719–4,184)
DST transducers and skin fittings
- Airmar — DST810 (depth/speed/temp.)
smart NMEA 2000 transducer with a gyro€350–480 (≈$407–558) - B&G / Raymarine — DST triducer
integrated sensor in a single housing€300–450 (≈$349–523) - Through-hull fitting + fairing block
mounting the transducer at the right angle€30–90 (≈$35–105)
The NMEA 2000 bus
- NMEA 2000 starter kit (backbone)
cables, T-pieces, 2 × 120 Ω terminators, power injector€60–120 (≈$70–139) - T-pieces and drop cables
extending the bus with further devices€10–30 (≈$12–35) / pc - 120 Ω terminators (pair)
male/female ends for the bus€12–25 (≈$14–29)
Sealing and installation
- Sika — Sikaflex 291 (marine sealant)
all-purpose polyurethane sealant for the deck€12–22 (≈$14–26) - MS polymer (flexible sealant)
isocyanate-free adhesive sealant€10–20 (≈$12–23) - Epoxy resin for sealing the core
protects the balsa or PVC core around the hole€20–45 (≈$23–52)
Safety and the electrical installation
- Emergency bungs (wooden plugs)
one set at every skin fitting€5–15 (≈$6–17) - Tinned marine cable (by the metre)
the right cross-section for supplying the electronics€2–5 (≈$2–6) / m - Watertight terminals, sleeving and fuses
heatshrink connectors and circuit protection€10–25 (≈$12–29)
Tools
- Hole saws (set) and a drill
the right diameters for the transducer and through-hulls€20–60 (≈$23–70) - Digital multimeter
measuring voltage, continuity and the bus resistance€15–50 (≈$17–58)