Mercruiser to E80 Classic wiring?

[vmaxhp]

I am attempting to add digital read out of my two Merc 2007 496 Mag engines. I have a 2007 Formula 34 PC with dual Mercs. I'd like to read RPM, Fuel Flow, etc at my E80 Classic display. Attached are the components I've put together to do so. Right now, the Starboard Engine displays under the Port Engine on the Twin Engine display panel, and the Port Engine doesn't register at all. When I went to my local Merc repair shop, I thought they had correctly set the engines for port/starboard. They also mentioned there's four positions -- inner and outer for each of port/starboard. To what engine position should the engines be set? Any other thoughts why this isn't reading correctly?
Thanks!
Rick