I installed a Garmin 2006 yesterday and it talks to everything--so
far. I see it is using NMEA version 2.3, and its only speed output is
in the GPRMC sentence.

This boat has the Yamaha engine management system that includes the
fuel management gauge. I understand the fuel management gauge accepts
NMEA inputs. Of course, there is little documentation of this, and
Yamaha has no customer service--other than to tell you to call your
clueless dealer.

The instructions (what little there are) tell you to flip a dip switch
to select NMEA for speed input, but it does not tell you which wire(s)
to use. DOH!

Has anyone hooked one of these rascals to a GPS to get MPG info?
Which wires are what?

Thanks in advance for your help.

Kurt