I want to show my engines' rpms on my Garmin 741sx. The Garmin is capabale of this (there is a specific screen), but I understand I will have to connect to the NMEA 2000 backbone. My Mercruiser 255s predate NMEA 2000 by a couple of decades, and I don't know how -- or if -- I can do this. Any good ideas? Do I need some sort of adapter?
