I have a small 16 foot center console boat. I fish on a great lake for walleye. I use a humminbird 898 mounted in the center console for navigation and sonar.
When trolling, I often face the stern to watch the rods and cannot see the 898 si display screen . I am very frugal (cheap). So i wanted a display mounted in the stern that would display sonar. Network feature and a second humminbird was out of my budget
After several reviews, I realized the best way to add a 2nd display, would be to use the VIDEO OUT feature of the 898.
I ordered the video cable from my humminbird dealer. I had a small 7" LCD screen used in automotive application. It is 12 volt and is pretty bright display. They can be found on ebay for @$40 - $99. The screen is not designed for marine. I also had a 16 foot RCA cable and some red/black power wire.
I wired the power ground to the same power ground wire as my humminbird. I plugged in the video out cable into the back of the Humminbird. I routed the cables to the stern. I connected my test display.
Here is a video showing a test run
http://youtu.be/o42osNnewlAMy next step is to paint the monitor housing light color (for heat) and to seal the housing for moisture