Aloha from Maui Hawaii. I recently bought a used GP7000F fish finder/plotter. It seems to work well, but recently a problem occurs. I tested the sonar on land before launching my boat and all worked well. When I turned it on after launching, the screen showed only white. None of the buttons worked and the only way I could turn off the screen was by unplugging the power. Every time I turned it back on the same thing occurred. I called tech support at Furuno and the tech told me to hold the "clear" button while turning on the machine. This worked, but to continue, you must delete all the RAM. I did this and the machine worked well. I spent about an hour and a half reentering my waypoints and settings. Two weeks later the screen went blank again. I held the clear and power on and it works again. This sucks if I have to reprogram every time. Does anyone know what is causing this problem and how to solve it? The tech could only suggest a power surge, but this is not what is happening.

Also, my owners manual says virtually nothing about how to use the sonar feature of this machine. Is there any literature available on how to use the various settings, e.g., signal level, and what they mean? How much fish data will I lose by adding the various filters? What actually IS the signal level referring to? Thanks for any input. :huh
I would recommend a low cost SD card to keep your points and routes backed up so you can restore them if this problem or something else happens. Just like with a PC, if you value the data, it is helpful to have a backup. If your unit keeps having issues with going WHITE (and your are using good clean power); I would recommend sending it into the Furuno service center for repair evaluation.
Thanks Johnny. I just ordered a SD card and will back up.. I contacted tech support at Furuno, and they basically said the same as you..