I purchased a 778c unit a couple years ago on-line. A significant savings over a purchase from a sporting goods store. The deal included a speed wheel for free. I received the unit without the speed wheel. The on-line company denied that the speed wheel was included. After several e-mails disputing their claim though they had renewed an advertisement indicating the speed wheel was free, they sent me the speed wheel. I then decided that it would be in my best interest to connect the unit to a battery (January) instead of waiting for the spring when I would put the unit in my boat. Connecting the unit to a battery, the unit would not power up. Contacted the seller, I returned the unit. They tested it sent it back, reporting that the unit powered up. I tried it a second time and it did not power up. Returned it a second time and then received it back with no explanation, but this time the unit powered up. Lessoned learned - I will never purchase marine electronics on-line. The cost of sending the unit back twice eliminated any cost savings from buying it on-line.