2001 sport nautique - faria GPS gauge

[TitanAir]

Hi all, looking for help/advice with replacing an old stock speedometer with a faria GPS speedometer. Initially, I hoped this would be an easy project with a few crimped wires (my nautique does not have perfect pass and I was hoping that I would not have to drill a hole in the boat).

My issue is in "matching" the correct wires (forgive me, I have no clue how to read wiring diagrams) and I have read the sticky threads on this repair, most showing how to replace using analog with PP.

Here is my scenario: there are four wires from the new gauge (violet/black/blue/yellow) and 4 from the dash of the boat (violet, black, blue grey); see attaced picture. I have matched black to black and violet to violet but have no clue what to do with blue and yellow wires. Any advice or help is appreciated!

[BigBen_UK]

Yellow should go to a fused permanent connection to the battery - but this looks optional and will probably just add time after "ignition on" to reacquire satellites, and the light blue to the lights circuit (dark blue) - I thought Grey was the tacho (Revs) signal wire - so that's got me stumped being attached to a Speedo and all - but I bet you the new gauge will work with just the two you have connected.

[MaineDR]

http://faria-instruments.com/site_manuals/IS0350c.pdf

Light blue is for the light. Wire that up to the dark blue from the boat so you can drive at night.

Yellow is the 'keep alive'. I'm not sure what the purpose of this is, but it may have to do with calibrating the gps like mentioned above. I don't think it is necessary. You would have to run a wire directly to the 12v terminal on your battery especially if you are running a perko and turn it off after every use like I do.

Grey isn't needed.