Connect a Victron Cerbo GX

Connect BoatKit to a Cerbo GX on the vessel's local network to use supported Victron power equipment, tank levels, and temperatures. Tank and temperature readings can arrive directly over Modbus TCP while the GX's NMEA 2000 output is disabled. No Victron cloud account or Internet connection is needed for these local readings after BoatKit setup.

Before you begin

• Connect the GX device and the BoatKit host to the same reachable local network. A native tablet host must be connected to the vessel's Wi-Fi with BoatKit active.
• In the GX Settings → Services, enable Modbus TCP for direct tank and temperature readings. The sensors must already be connected and configured in Venus OS.
• Enable local MQTT access for the broader power integration and for full temperature identity and NMEA forwarding metadata. If the GX uses a protected local security profile, have its local network password available.

The local password is separate from a Victron Remote Management account password. BoatKit's integration settings do not enable GX services for you. See Victron's Modbus TCP guidance for GX service settings and network requirements.

Connect and confirm readings

1. Open Settings → Integrations and enable Victron Cerbo GX.
2. Check the Cerbo GX Connection status. Supply the Cerbo GX Network Password if requested for protected MQTT access.
3. Check the separate Modbus sensors status and discovered tank and temperature counts. Common sensor instances are discovered first; other instances can take several minutes.
4. Open Settings → Sensors. Look under Tank Levels and Temperature for the GX sensors and confirm their values against Venus OS.
5. Open a sensor's settings to rename it, adjust smoothing, configure warnings, or override a tank's reported capacity. Use its row checkbox to control whether BoatKit uses it.

Temperature services are exposed by default. The connection panel also offers an exposure checkbox for each discovered temperature service. MQTT and Modbus readings from the same unambiguous Venus instance use one temperature sensor.

The readings use BoatKit's normal sensor models, so enabled sensors are available for dashboard selections, history, and configured warnings. Names, capacity choices, warning settings, and explicit unlink choices are included in portable vessel backups.

Duplicate NMEA 2000 sources

BoatKit automatically combines a direct tank with its NMEA 2000 source when the GX forwarding configuration identifies exactly one matching Victron NMEA device. The direct GX tank remains the displayed sensor. Either fresh provider can keep it active if the other disconnects. Existing NMEA tank settings are retained when the direct tank has no settings of its own. Saved gauges, history references, and configured watermaker tank selections continue to follow the linked tank.

For Ruuvi temperatures mirrored through Signal K, BoatKit uses the existing full hardware identity and configuration matching rules, with a conservative exact reading correlation fallback. Full identity requires MQTT metadata. Similar names, matching tank instances, and similar readings do not prove that two sensors are the same. Native GX NMEA forwarding does not expose auxiliary Bluetooth, analog, or USB temperature sensors; see Victron's NMEA 2000 integration guide.

A linked sensor shows its second source in Sensors. Open Source Links and choose Unlink to keep that pair separate. Allow automatic linking removes that exclusion; BoatKit still requires identity evidence before combining them.

When forwarding metadata is unavailable or ambiguous, sources remain separate. Some legacy Modbus unit addresses can refer to either a same-number Venus instance or a higher aliased instance. Those readings have separate identities and are excluded from automatic matching with MQTT or NMEA sources.

Connection problems

Symptom	What to check
GX is not discovered	Confirm the BoatKit host can reach the GX on the local network. Routed networks and VLANs may block discovery or service access.
Modbus sensors report a connection error	Enable Modbus TCP in GX Settings → Services and check local firewall access. MQTT credentials do not enable Modbus.
MQTT requests a password	Supply the GX local security-profile password, then check the separate MQTT status. Modbus sensors can continue independently.
A sensor is missing	Confirm Venus OS shows a supported tank or temperature service, allow discovery to complete, and check temperature exposure and sensor enablement.
A sensor becomes inactive	Check its Venus OS sensor status and connection. Faulted Modbus readings are not treated as valid zero values. BoatKit reconnects automatically.
Two sources remain separate	Check MQTT access and GX forwarding configuration. BoatKit keeps uncertain or explicitly unlinked pairs separate.

Supported power measurements appear in BoatKit's power-system settings and views. Available controls depend on the connected equipment and configuration; see Generator automation for generator control and optional GX AC-input timing. Zero solar production at night is normal. BoatKit support is independent of Victron Energy and does not replace Venus OS configuration or Victron installation instructions.