Is this the floscan you are thinking about?
There is also one with gps interface that will give nautical mpg when interfaced through your gps
Gas Model Features
Fits most gas engines rated from 25 hp to 2000 hp. Twin gas models available.
Microprocessor based electronics with 2-stage adjustable calibration of GPH & gallons used for superior accuracy.
Simultaneous independent display of Engine Hour Time, RPM, GPH, and gallons consumed.
RPM readout accurate to 10 RPM. Easily connects to existing tach signal wires.
GPH and Totalizer readings displayed in tenths of a gallon. Totalizer capacity up to 99,999 gallons.
Dual color (amber/green) backlighting of LCD provides for easy night viewing.
Requires 1 Momentary ON / Constant OFF toggle button switch for resetting fuel totalizer reading. See Accessories page for recommended push button switch (4001-433-00) for this feature.
Twin gas models also incorporate an Engine Synchronizer Indicator and Port/Stbd GPH selection. 2 additional SPST toggle switches are required for accessing these features. See Accessories page for recommended toggle switch (4001-434-00) for these features.
Meter fits 3-3/8" panel opening (standard tach size). Can replace existing tachs in panel.
Models available in black or white (bezel/dial face).
Uses Model 20A, 2OB, 231, and 233 Series flow sensors designed for gas engines.
Applications
Fits all carbureted inboard and stern drive engines up to 350 hp.
Fits all EFI inboard and stern drive engines (including Mercruiser and Volvo) with closed loop fuel return systems.
Fits all Mercury Optimax, Evinrude Ficht, Yamaha HPDI, and Honda 4-stroke engines.
Fits all 2-stroke EFI outboard engines.
Linear Mode
