Complete Engine Monitoring for Boats

Build a complete engine-monitoring dashboard with 8 gauges: 4× Temperature (DS18B20) + 1× Tachometer (RPM) + 1× Oil Pressure + 1× Fuel Tank Level + 1× Engine Hours. All sensors feed a single ESP32 running ESPHome, visualised in Home Assistant.

• 4× Temp gauges
• 1× Tachometer
• 1× Oil pressure
• 1× Tank level
• 1× Engine hours

🧭 What You’ll Build

• One ESP32 “remote hub” that reads multiple sensors (1-Wire, I²C, pulse) in the engine bay
• 8 total gauges: 4× temperature (raw-water elbow, alternator, coolant area, thermostat), 1× tachometer (RPM), 1× oil pressure, 1× fuel tank level, 1× engine hours
• Color-coded needle gauges, history trends, and alert automations (siren/horn/notifications)
• A scalable pattern to add more sensors over time (additional DS18B20s / INA219s)

🧩 System Architecture

• Sensors → ESP32: DS18B20 (1-Wire), INA219 (I²C), alternator tacho via optocoupler (pulse)
• Firmware: ESPHome on the ESP32 (OTA updates)
• Backend: Home Assistant on Raspberry Pi (entities, templates, dashboards, automations)
• Power: 12 V → 5 V DC-DC buck to ESP32; 3.3 V rails for sensors

💡 Practical wiring pattern

• Use a screw-terminal breakout for the ESP32 to make engine-bay wiring robust
• Route all DS18B20s to a single data pin with one 4.7 kΩ pull-up
• Put INA219s on SDA GPIO21 / SCL GPIO22; up to 8 per ESP32 with unique addresses
• Feed alternator W/stator/tacho to a 24 V optocoupler module → ESP32 GPIO25 (pulse counter)

🧰 Consolidated Parts & Tools

• ESP32 dev board (30-/38-pin) + screw-terminal breakout/enclosure
• DS18B20 waterproof probes (1–5+ as needed) + 4.7 kΩ resistor (single pull-up for the bus)
• INA219 modules (for oil sender & fuel sender; supports more tanks/senders)
• Optocoupler input module (24 V recommended) for alternator tacho
• Wiring: Dupont leads, double spade adapters, cable ties, strain relief
• Power: 12 V → 5 V DC-DC buck (boat install) or USB (bench)
• Optional alert devices: siren/horn, lights; optional relay for alternator cooling strategy

🚀 Build at a Glance

1. Provision an ESP32 in ESPHome; confirm OTA and logs work.
2. Add modules one by one:
   • DS18B20 temperature bus on GPIO25 with 4.7 kΩ pull-up → discover addresses (aim for 4 probes → 4 gauges)
   • INA219 on I²C (SDA 21, SCL 22) → read sender voltage (oil & fuel)
   • Optocoupler from alternator W/stator/tacho → ESP32 GPIO25 pulse counter
3. Use the YAML snippets for each module (links below).
4. Calibrate (voltage→pressure, voltage→% full, pulses→RPM) using your engine’s values.
5. Create HA dashboards (needle gauges, severity bands) and add alert automations.

🧱 Modules (Start Here → Then Open Each Full Guide)

📎 Series links (quick list)

• Engine Temp Monitoring
• Oil Pressure Monitor (ESP32 + INA219)
• Digital Tachometer (ESP32 + Optocoupler)
• Fuel Tank Gauge (ESP32 + INA219)

📟 Dashboards & Automations

🛠️ FAQs & Troubleshooting

DS18B20 shows as “unknown”

• Copy the discovered address from logs and replace the placeholder in YAML; check the 4.7 kΩ pull-up and bus wiring

INA219 reads 0.0 V

• Confirm I²C pins (SDA 21, SCL 22) and that VIN+ is on the sender’s “Gauge” terminal

RPM unstable

• Verify alternator W/stator tap, optocoupler polarity, grounds; add another calibration point; keep wires short

📰 Featured by PBO

Read the Practical Boat Owner article covering this end-to-end project:

Read on PBO

Then return here and follow the modules above to build your own system.

⚠️ Disclaimer

The information provided is for educational and informational purposes only. Perform all installations safely and correctly; consult a licensed professional for boat electrical work. Use at your own risk.