I've been running 2 units on my dash for 10 yrs. 3 units now since the raymarine only gets used part time.. see other post. when running around the islands etc I run both as gps with depth displayed digitally on the screen. one zoomed in to 1 to 2 miles the other zoomed out to 8 miles. this way I can stay on track for where I'm going to start looking for fish and make sure I don't get to close to any of the reefs. also when it gets nasty out there. much easier to stay on course with shorter glances at the screens as my eye sight sucks then I switch to fishfinder when I'm ready to start looking for fishable fish.