⚓ Master Marine Electronics Toolbox

Ohm’s Law (V, I, R, P)

AC Sine Converter

dB Converter

Battery Runtime

Cable Voltage Drop

NMEA 0183 Checksum

Sentence Checksum

Formula Library (Extended)

1. Electrical Power & Energy

Formula	Meaning
V = I × R	Voltage (Volts)
P = V × I	Power (Watts)
E = V × I × t	Energy (Watt-hours), t in hours

2. Voltage Drop

Formula	Meaning
Vdrop = (2 × L × I × Rcable) / 1000	Vdrop: Voltage drop (V), L: One-way cable length (m), I: Current (A), Rcable: Resistance per km (Ω) Keep DC drop under 3% for sensitive electronics.

3. Battery Bank Calculations

Formula	Meaning
AH = (Load (W) × t (hours)) / (V × η)	Ah required; η = system efficiency
Ctotal = C1 + C2 + ...	Parallel battery capacity sum
Vtotal = V1 + V2 + ...	Series voltage sum

4. RF & Antenna Basics

Formula	Meaning
λ = 300 / f	Wavelength (m), f in MHz
D ≈ 1.17 × √h	Antenna horizon distance (nm), h in m
Dtotal = D1 + D2	Total horizon for two antennas
Pout = Pin × 10-LossdB × L / 10	Coax power after loss

5. Sonar / Depth Sounder

Formula	Meaning
Depth = (v × t) / 2	v: Speed of sound (~1500 m/s), t: Round-trip time (s)

6. Conversions

• Knots → km/h: × 1.852
• Nautical miles → km: × 1.852
• Nautical miles → miles: × 1.151
• Feet → meters: × 0.3048

7. NMEA 2000 Cable Load

Formula	Meaning
Imax = (Psupply - Pload) / Vdrop	Max current backbone can handle

Learning & Reference

1. Power & Electrical Basics

Term / Abbrev.	Meaning	Quick Notes
DC	Direct Current	Common: 12 V, 24 V for vessel systems.
AC	Alternating Current	Shore power: 110 V or 230 V (50/60 Hz).
Ground/Earth	Common return path	Avoids shock & interference; use proper bonding.
Bus Bar	Common connection point	For positive/negative feeds.
Breaker / Fuse	Overcurrent protection	Match to device load + cable rating.

⚠ Tip: Corrosion is a major cause of faults — check for green/white powder on connectors.

2. Common Marine Electronics Systems

System	Function	Notes / Brands
GPS / GNSS	Positioning	Standalone or integrated into MFD.
Radar	Target detection	Magnetron or solid-state; attention to warm-up time.
AIS	Vessel ID & position exchange	Class A (ships), Class B (pleasure craft).
VHF Radio	Marine comms	DSC-enabled sets require MMSI.
Depth Sounder / Sonar	Depth & seabed profile	Transducer mounting critical.
Autopilot	Heading hold & track following	Uses compass + rudder feedback.
Chartplotter / MFD	Navigation	Integrates GPS, radar, sonar, AIS.
EPIRB / PLB	Emergency beacons	406 MHz to Cospas-Sarsat; test regularly.

3. Data & Networking Standards

Standard	Purpose	Key Notes
NMEA 0183	Serial data link	ASCII sentences, 4800 bps (or higher for AIS).
NMEA 2000 (N2K)	CAN-bus marine network	250 kbps, plug-and-play, T-connectors & terminators.
Ethernet	High-speed data	Used for MFD video/radar; Cat5e/Cat6 marine-rated cable.
SeaTalk / SeaTalkNG	Raymarine proprietary	NG is NMEA 2000-compatible.

4. Key Troubleshooting Steps

• Check Power – Battery voltage, breaker/fuse, polarity.
• Inspect Connections – Clean, tight, corrosion-free.
• Test Cables – Continuity & insulation resistance.
• Check Settings – Baud rate, network IDs, GPS mode.
• Firmware Updates – Fixes many bugs; ensure correct version.
• Cross-Test – Connect device to known-good network/system.

5. Marine Cable & Connector Quick Guide

Cable Type	Use	Tip
Tinned Copper	All marine wiring	Corrosion-resistant, flexible.
RG-58 / RG-213	VHF coax	Keep under 15 m for RG-58 to reduce loss.
NMEA 2000 Backbone	Data bus	120 Ω terminators at each end.
Shielded Twisted Pair	NMEA 0183	Reduces interference.

6. Quick Safety Reminders

• Isolate power before servicing.
• Use marine-rated fuses and breakers.
• Keep electronics dry and ventilated.
• Always label cables when removing.
• Test alarms (bilge, fire, gas) regularly.

Safety & Standards

1. General Safety

Area	Key Points
Electrical Isolation	Switch off breakers or disconnect batteries before servicing. Use lock-out tags if working in teams.
PPE	Safety glasses, insulated gloves for DC/AC, hearing protection near radar or engines.
Radar Safety	Stay outside beam when transmitting; magnetron radars can cause harmful RF exposure.
Fire Safety	Keep Class C (electrical) extinguisher accessible; never use water on live circuits.
Environment	Ensure ventilation; avoid humidity and condensation when panels open.
Tool Safety	Use insulated tools; avoid dropping metallic tools near terminals or bus bars.

2. Electrical & Installation Best Practices

Topic	Best Practice
Cable Selection	Always use marine-grade tinned copper wire per ABYC / ISO sizing charts.
Fusing & Protection	Fuses or breakers within 7 inches (18 cm) of battery positive unless cables in conduit.
Connections	Use crimped terminals with adhesive heat shrink; soldering discouraged in high-vibration environments.
Bonding & Grounding	Follow vessel bonding plan; avoid ground loops in electronics.
Corrosion Prevention	Apply dielectric grease to connectors; avoid mixing metals without isolation washers.
Labeling	Clearly mark cables and devices; keep wiring diagram onboard.

3. Key Marine Standards & Guidelines

Standard / Code	Purpose
IEC 60945	Maritime navigation and radio equipment requiring environmental tests.
IEC 61162	Digital interfaces (NMEA 0183/2000 equivalents).
IEC 62288	Navigation info presentation on shipborne displays.
IMO SOLAS	Safety of Life at Sea – equipment carriage and emergency gear.
GMDSS	Global Maritime Distress and Safety System requirements.
ABYC E-11	AC & DC systems on boats – wiring, protection.
ISO 10133	DC systems on small craft.
ISO 13297	AC systems on small craft.
MARPOL Annex I	Pollution prevention sensor/electrical requirements.
STCW	Training standards for marine electrical & radio operation.

4. Offshore-Specific Reminders

• Always log equipment servicing in maintenance records.
• Carry spares & redundancy: fuses, connectors, short cable lengths.
• Follow manufacturer service manuals – radar, GPS, autopilot test modes.
• Respect class rules (Lloyd’s Register, DNV, ABS) when applicable.