Camoman
I use 480's and had love them. The best advice I can give is to look in the owners manual, it does tell you how to change to settings to get the arches and in the troubleshooting portion, you will find the bubbles on the screen listed and different things to check to try and fix it.
They also have a web site you can down load and play around with the settings without actually having to attach it to the boat.