Fuel Flow Sensor - Water Flow Sensor

Some years ago I bought an old motor boat with very basic instruments on the console. The fuel gauge was so unstable during cruising that I barely distinguished between full and half tank. Then suddently the fuel level sensor stopped working and it was impossible to replace.

Fuel management is one of the most important task on a motor boat.

Dispite several devices available on the market, I decided to build a small counter of fuel liters through an Arduino UNO and a flow meter. The software upgrade from a simple flow meter to an econometer was very short and the device became a fuel level meter and marine econometer, able to measure liters/hour while setting throttle, pitch and trim to minimize the fuel consumption over the boat speed.

https://youtu.be/C1YyB6J1ifk?si=Lk5zJDjZH8jAOd7q

Since I was quite satisfied with that sensor coupled with a lcd 4x20 display, I decided to upgrade the system to include a touchscreen, a GPS, trim sensor, throttle position, and boat pitch...

https://youtube.com/shorts/D3eOutZOpVg?si=kltiyWjdtAzZNvPb

https://youtu.be/0HsfpaqQn2M?si=f-0DaIC1zfwzFmbv

After first trials I recognized that backlighting of 200/300 nit of my Nextion display is not the best during sunny days on an open boat, so I start playing with a bluetooth connection to the smartphone, tipically equipped with 1000/1300nit display. Under Android the scenario changes completely with the possibility to calculate distances, waypoints on a map, record and recall data... It was funny to develop my first app.

https://youtube.com/shorts/z2h2maR6PME?si=WNOqkWI0LZ1tgqIq

However, the key element of the system is the flow sensor and it's calibratiion. There are several type on the market depending on the flow rate. To select the sensor, you need to know the engine's maximum consumption in liters per hour. Pressure drop should be between 0.05 and 0,1 bar.

This instructon is focused on DIY fuel flow sensor. The sensor here described is tested between 1.8 liter/h up to 30 liter/h with max pressure drop of 0,08 bar. The range should be extended by replacing or removing the nozzle inside.

For my small Evinrude eTEC 90HP 30 liter/h is enough.

Of course the sensor can be used for other engines, cars, motorbikes ect.

The sensor shall have different outputs:

1. Bluetooth
2. Serial TTL, I2C, SPI
3. NMEA2000
4. Analogic signal 0 - 12V
5. Square signal (in this case MCU is not needed)

ITEM Qty Description Link

1 1 Upper Housing https://www.printables.com/model/1887225-upper-and-lower-housing-for-fuel-flow-sensor

2 1 Lower Housing https://www.printables.com/model/1887225-upper-and-lower-housing-for-fuel-flow-sensor

9 1 Turbine https://www.printables.com/model/1887225-upper-and-lower-housing-for-fuel-flow-sensor

3 2 Brass fitting M8x1 x 8mm https://s.click.aliexpress.com/e/_c33wHbVV

4 1 Cable terminal ---

5 1 3A MINI DC-DC STEP DOWN CONVERTER VOLT REGULATOR 5V-23V TO 3.3V 6V 9V 12V

6 1 A3144 Hall Switch Effect Sensor

7 1 Microcontroller ESP32-S3

8 1 Small magnets Diam 2mm x 1mm h

10 2 O-ring OD:10.5mm, sez: 2mm

11 1 8x1,5mm Cylindrical Pin 304 Stainless Steel https://s.click.aliexpress.com/e/_c37zlBhz

3d printing is a tricky technology for this watertight application because normal 3D print leaks. The setting of the machine and slicer shall be quite delicate to make layers properly sealed. Of course the setting has a direct impact on tollerances.