Instruments that won't wake up, an autopilot throwing a 'low voltage' warning, or devices dropping off the network are almost always a power or connection problem — not a failed unit. A multimeter and ten minutes will usually find where the volts are being lost.
What you'll need
- A digital multimeter set to DC volts.
- Ideally, a long test lead run back to the battery negative to use as a clean reference — this rules out earth/ground faults.
- Your system wiring diagram, so you know where power is fed in.
Safety first: this is low-voltage DC work, but treat the electrical panel with respect, isolate circuits before disturbing wiring, and re-fuse to the correct rating.
Know your network
Raymarine uses two network types, wired differently:
- SeaTalk (classic, 3-wire): a red +12V wire, a bare screen / 0V, and a yellow data wire. Power and data share the same cable, so a poor connection can take out both.
- SeaTalkng (5-wire): a backbone carrying a power pair (red +12/24V and black 0V), a data pair, and a shield. Power is injected at a single point through a fused power cable. Every device spurs off that backbone.
The method: follow the volts
- Confirm the supply. At the panel, measure the breaker or fuse output. You should see full battery voltage — around 12V (or 24V on a 24V system). No voltage here means a switch, fuse, breaker or supply fault, and the rest of the network is innocent.
- Measure at the power insertion point. On SeaTalkng, measure red → black at the power cable; on SeaTalk, red → screen. It should read close to supply voltage.
- Work along the network. Take the same reading at successive connectors, moving away from the power tap. Voltage should stay close to supply everywhere.
- Find the drop. Where the reading falls away noticeably, the fault — corrosion, a bad crimp, a broken conductor, or an undersized feed — lies between that point and the last good reading.
- Check your reference. Repeat a suspect reading using the lead run back to battery negative. If the voltage is suddenly correct against the battery but wrong against the local screen/black, you've found a bad earth/0V connection.
Catch the faults that only show under load
A corroded or loose joint can read a perfect 12V with nothing drawing through it, then collapse the moment the system tries to power up. To expose these, take readings while the system is attempting to start, or place a small 12V bulb (around 5W — not an LED) in parallel with your meter to put a light load on the circuit. A reading that sags under that load is a high-resistance connection.
Autopilots need two power checks
A SmartPilot or Evolution course computer has two power inputs: the high-current supply that drives the linear or hydraulic drive, and the network supply for SeaTalk/SeaTalkng. Check both. A frequent mistake is trying to power a whole SeaTalkng backbone from the course computer's network spur — the pilot computer isn't designed to feed the entire bus and the voltage will sag. Power the backbone from its own fused feed, and confirm the drive supply is delivering full battery voltage under load.
Reading the results
- Full voltage at the panel but low at the devices — voltage drop in the cabling or connections. Suspect long runs, undersized cable, corrosion, or a single power tap feeding too much backbone.
- Nothing at the panel output — breaker, fuse, switch or supply fault.
- Good voltage but a single device is dead — that device or its own spur cable, not the network.
The usual culprits
SeaTalk and SeaTalkng power faults are almost always a cable or connection issue: corroded 3-pin SeaTalk connectors, water sitting in a plug, a tired inline fuse, loose spade terminals, or an undersized power feed on a long backbone. Disconnect suspect connectors and inspect each pin with a magnifier before replacing any hardware.
What to do next
If you've traced the loss to a cable or connector, we stock genuine Raymarine network power cables and connectors, including the SeaTalkng-to-SPX moulded power cable, and course computers such as the SPX-SOL SmartPilot course computer if the unit itself is at fault. Send us your readings and we'll help you interpret them.
This is a general troubleshooting guide. Expected voltages and wiring vary by product and installation — always confirm against your specific Raymarine manual, and if you're unsure, contact Hudson Marine Electronics or a qualified marine electronics engineer.
