Hi, I'm new here, but just noticed your post. I recently purchased an older 2000 Signature 260, and couldn't figure out why batteries kept discharging with all power turned off and the shoreline disconnected until I found that the refrigerator had a direct connection to the batteries.
We are in Discovery Bay and have been cruising the Delta for quite some time. Biggest problem I find now is the intrusion of weeds. It's something new that has occurred in the last eight or nine years. I didn't know Navionics had an app for the iPhone, so I will check it out. Thanks for the post.