Remote Boat Monitoring: Sensors, GSM Alarms and Victron VRM
You can see your moored yacht's battery voltage, bilge level and shore power status from your phone, provided you choose the right sensors, gateway and alarm thresholds.
Remote boat monitoring lets you see the battery voltage, bilge level, shore power status and cabin temperature of a yacht left in a marina or on the hard, straight from your phone. Set up correctly, it flags a problem before the battery is flat or the bilge overflows. In this article we cover sensor selection, the difference between simple GSM alarm units and Victron VRM-based systems, and what to watch for during installation.
What should you monitor?
The values worth monitoring are similar on every boat; what differs is how thresholds and priorities are set for the vessel. The table below is a starting point for a typical motor yacht or sailing yacht:
| Monitored value | Sensor / source | Alarm logic |
|---|---|---|
| House battery voltage and state of charge (SoC) | Shunt-based battery monitor | On a 12 V system e.g. below 12.0 V or below 50% SoC |
| Start battery voltage | Battery monitor's auxiliary input | Significant drop |
| Shore power present | Inverter/charger AC input or AC relay | Immediately on AC input loss |
| Bilge level | High-water float switch | When high level is reached |
| Bilge pump cycle count | Digital input from pump supply | Unusually frequent cycling |
| Cabin temperature and humidity | Wired or wireless sensor | Frost risk, excessive humidity |
| Fridge / freezer temperature | Temperature probe | Threshold exceeded |
| Door, hatch contact, motion | Magnetic contact, PIR | Opened while the boat is unattended |
| Position | GPS | Leaving a defined area |
The bilge float switch and pump monitoring are especially important: frequent pump cycling is an early sign of a leak. We cover this in detail in our article on bilge pumps and alarm systems.
Two approaches: GSM alarm unit and GX + VRM
Simple GSM alarm unit
Compact alarm modules with a SIM card work with a few digital inputs and a temperature sensor. When an input triggers, they send an SMS or place a call. Their strengths are low consumption, simple installation and no need for internet. Their limitation is that they offer no detailed data, history or graphs: you get a "battery low" message but cannot see why.
Victron GX device and the VRM portal
In the Victron Energy ecosystem, a GX device such as the Cerbo GX collects data from the battery monitor, inverter/charger, MPPT solar charge controller and other components, and sends it over the internet to the VRM portal. With VRM you can:
- Monitor battery voltage, current, SoC, solar yield and AC input status live and historically,
- Receive email and app notifications based on thresholds you set,
- View and adjust the GX screen remotely with Remote Console,
- Analyse consumption patterns with daily and monthly energy reports.
Depending on the model, GX devices offer digital, tank and temperature inputs, and supported wireless temperature sensors can also be added. A GX device can also connect to the NMEA 2000 network to show battery and energy data on multifunction displays; we explain the network rules in our NMEA 2000 installation guide.
In practice many yachts use both approaches: VRM for detailed analysis, and an independent GSM alarm unit as a backup channel for the critical bilge alarm.
Internet connection: the weakest link
Remote monitoring is only as reliable as its connection. Marina Wi-Fi often slows down or drops out at the height of the season. Our recommended setup:
- Make a 4G/5G router with a data SIM, or an LTE modem suited to the GX, the primary link.
- Improve signal strength with an external antenna; on steel or carbon hulls the difference is marked.
- Power the router and GX device from DC so the link does not drop when the inverter is off.
- Check the SIM's data plan and roaming settings for your cruising area.
Our article on internet on board and Starlink installation will help with router choice and antenna placement.
Power supply and consumption
The monitoring system has to keep working while the boat is unattended and the main switches are off. It is therefore usually fed from a separate circuit ahead of the main switch, protected by its own fuse. Standards such as ABYC and ISO 13297 allow certain circuits, such as bilge pumps and alarms, to be connected this way, but the circuit must always be fused close to the source.
A GX device and 4G router together typically draw a continuous load of a few watts up to around 10 W. On a 12 V system, a continuous 6 W load equals roughly 12 Ah per day. On a boat without shore power, that adds up to significant capacity within a week. Without solar input, it makes sense to switch the router off at low voltage and leave only the GSM alarm running.
Common mistakes
The mistakes we meet most often in the field are the ones that leave a system installed but useless:
- Treating voltage as state of charge: on lead-acid batteries, voltage is misleading under load and while charging. On LiFePO4 the voltage curve is so flat that there are only a few hundred millivolts between 20% and 90%. Reliable alarms need a shunt measurement.
- Wiring the high-water alarm to the pump's float switch: if that float fails, the pump and the alarm are lost at the same time. The alarm must always have its own, higher-mounted switch.
- Skipping the shore power alarm: in a marina, a plug working loose or a tripped residual current device is common. The charger stops and the fridge drains the battery within a few days.
- Sending notifications to one person only: an alarm that reaches an owner who is abroad may reach no one. The captain, marina staff or service team should also be on the notification list.
- Remote firmware updates: updating inverter or GX firmware with nobody on board can leave the system unreachable if something goes wrong. Do updates on board where possible.
Installation steps
- Assess needs: how long is the boat left unattended, is shore power available, which risks come first?
- Measure the battery properly: voltage alone is not enough; a shunt-based battery monitor (such as the SmartShunt) gives accurate SoC and current.
- Place the sensors: mount the high-water switch above the pump's float switch, and the temperature sensor out of direct sunlight.
- Set up the connection: feed the router, antenna, SIM and GX device from the DC circuit.
- Set alarm thresholds: thresholds that are too tight create false alarms, too loose and warnings come late. Watch the data for the first two weeks and fine-tune.
- Test: cut shore power, lift the float by hand and confirm that the notification arrives.
- Secure access: change VRM and router passwords, use two-factor authentication where possible, and share access only with those who need it.
Work with Aslan Yacht on remote monitoring
From our workshop in Turgutreis we install GX devices and battery monitors, wire sensors, integrate routers and configure alarms at marinas around the Bodrum peninsula. To review your energy system and monitoring needs together, take a look at our electronics and navigation service or contact us directly.
Frequently asked questions
Will a remote monitoring system drain the batteries?
A properly installed system draws a continuous load of a few watts. Without shore power, that load must be budgeted against bank capacity and any solar input, and non-critical devices should be switched off automatically at low voltage.
Is marina Wi-Fi good enough for remote monitoring?
Not on its own. Marina Wi-Fi can be intermittent and delay alarms. A 4G router or GSM module with a data SIM should be the primary link, with Wi-Fi used only as a backup.
Does all my equipment need to be Victron to use VRM?
No. It is the GX device that sends data to VRM. Victron battery monitors, inverters and chargers integrate best, but supported temperature, tank and digital inputs let you monitor other brands' equipment as well.
