hey,
Lucky you as i had one of these for my first fish finder units, which i still have the manual on my shelf! Cant say much about the unit tho
I think your only option is to reset as would most units. It says "reset options does not erase any wayspoints, routes, plots trails or sonar logs" So why not.
Let me know if you need instructions to reset. I take a pic and post it up for you.
cheers