Complete Engine Monitoring for Boats

Complete System

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

Engine dashboard with 4 temperature gauges, tachometer, oil pressure, fuel tank level, and engine hours

As featured in PBO: How I installed a smart engine monitoring system on my sailboat .

🔗 Overview · Architecture · Parts · Quick Steps · Modules · Dashboards & Automations · FAQs

🧭 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

Provision an ESP32 in ESPHome; confirm OTA and logs work.
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
Use the YAML snippets for each module (links below).
Calibrate (voltage→pressure, voltage→% full, pulses→RPM) using your engine’s values.
Create HA dashboards (needle gauges, severity bands) and add alert automations.

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

Engine Temperature (DS18B20)

✅ 4× temperature gauges (raw-water elbow, alternator, coolant area, thermostat)
✅ 1-Wire bus on GPIO25, 4.7 kΩ pull-up
✅ HA gauges + alternator > 100 °C alert

Open Full Guide · Dallas/DS18B20 YAML

Oil Pressure (INA219)

✅ 1× oil-pressure gauge (volts → bar, two-point calibration)
✅ Tap sender “Gauge” terminal → INA219 VIN+
✅ I²C: SDA 21, SCL 22

Open Full Guide · Oil Pressure YAML

Digital Tachometer (Optocoupler)

✅ 1× tachometer gauge (pulse counter → RPM)
✅ Alternator W/stator/tacho → optocoupler → ESP32 GPIO25
✅ Includes: engine_hours (counter); optional engine_active

Open Full Guide · Tachometer YAML

Fuel Tank Level (INA219)

✅ 1× tank-level gauge (volts → % full)
✅ Sender “Gauge” terminal → INA219 VIN+
✅ ESPHome exposes Tank Sender Voltage; HA template maps volts → %

Open Full Guide · INA219 Voltage YAML · Tank % Template YAML

📎 Series links (quick list)

📟 Dashboards & Automations

Gauges

✅ Total: 8 gauges → 4× temperature + 1× oil pressure + 1× RPM + 1× tank level + 1× engine hours
✅ Temperature gauges (needle) with severity: e.g., yellow 30 °C, red 42 °C at the raw-water elbow
✅ Oil pressure 0–5 bar (needle), green ≈ 3, yellow 4, red 0
✅ RPM 0–2400 with idle/amber/red bands
✅ Fuel level 0–100 % with low-fuel alert
✅ Engine hours counter (display card)

Automations

✅ Alternator > 100 °C → siren; optional relay to reduce field current
✅ Low oil pressure → horn/notification (gate by engine_active)
✅ Overspeed (RPM > threshold) → alert
✅ Low fuel (%) → notify before departure

History & Insight

✅ Compare last week’s engine temps to learn “normal” operating ranges
✅ Track oil pressure vs. RPM to spot wear or viscosity issues
✅ Correlate fuel usage with typical cruise RPM

🛠️ 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.

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