I was looking at the SR 161 at Jack Rabbit Marine. Don't have the appetite for a big expenditure since I don't know if my charting system is compatable nor if it will interface with my Raymarine 520 HS (I assume it won't). Anyhow, anyone using this puppy or something similar? I am in a major port with shipping lanes that look like the 405 freeway at rush hour sometimes, and it would be nice to figure out locations of the shipping. Actually, the big boys usually give a big echo on the radar, so it isn't a critical need, but the price is such that it may be worth playing with. My charting program is a commercial one about a dozen years old that went toes up, but runs like a champ and is wickedly powerful (if I can ever figure out the manual). Rick D.