Blue Sea Systems M2 OLED Tank Monitor

The Blue Sea Systems M2 OLED Tank Monitor tracks fluid level — fresh water, waste, or fuel — in up to four separate tanks from one compact display, with auto-calibration that adapts to each tank's unique shape rather than assuming a simple linear fill curve.

Key features

• Monitors tank volume in up to 4 tanks, 1% resolution
• Auto-dimming, bright OLED display, easy to read day or night
• 80dB alarm for high and low tank levels
• Isolated MOSFET relay for external circuit control
• Compatible with common sending units

Auto-calibration is the standout feature here — rather than assuming every tank fills in a straight line from empty to full, this monitor learns the actual shape of each tank during setup, giving a genuinely accurate reading even on irregularly shaped tanks common in tight bilge or hull spaces.

⚠️ Note on weight: an independent retailer spec sheet lists this unit at 0.25 lb, a much lighter and more plausible figure for this compact display than a 4 lb workbook entry that appears to duplicate the weight of the larger M2 DC Multimeter (PN 1830) — this is treated as a data entry error, and the corrected 0.25 lb figure is used here. Blue Sea recommends its own PN 1810 tank sender for best compatibility with this monitor.

Because the relay can be tied to any measured tank level, it's a practical way to trigger an automatic high-water alarm on a waste tank or a low-level warning on fresh water, rather than relying on someone remembering to check a gauge manually.