If fuel flow is your concern you might look into the Lowrance EP-10 which
is
an NMEA 2000 fuel flow device which inputs data to Lowrance displays.
Perhaps other displays as well??? It's cost is about US$ 50. It is a
turbine device which taps into the fuel line going to the engine.

Anything other than the Lowrance EP-10? It would appear they're using their
own form of NMEA cabling. While adapters do appear to be available it sort
of makes sense to just use stuff that's got standard Micro-C connectors on
them already.

There is
also an EP-15 which converts fuel level to NMEA 2000 data. It hooks up to
the sending unit and also reads out on a Lowarance display.

Does this work with the existing way the tank level is monitored? As in, am
I just patching into the wire, not installing something else in the tanks?