So like the title says, any time the boat goes over 12-15 mph the unit loses bottom in 2D sonar and will read a really high number (1,000+ feet). Already updated to the latest software (1.94) and set max depth to 30 feet for water 15-25 feet deep per HBird suggestion. Problem persisted.
I am quite certain it is a head unit issue. There is an old transducer on the other side of the transom (XNT 9 20T) that is compatible with the Helix 7. When connecting that transducer to the Helix 7, it does the same thing and loses bottom. If I hook it up to an old Humminbird head unit I have, the old unit is able to read and maintain the bottom signal fine. So it seems to be a head unit issue with the Helix 7.
Any ideas on what might be going on?