Garmin 178c GPS / Sounder Indications?

I have a garmin 178c that has been working great. This weekend something happened that I have never seen before. When operating normally, at rather same depth bottom countours, all of a sudden the Numeric depth Indication will start to flash...and after a period of time will go blank... After several minutes, it will indicate correctly again... Can't find anything in the Owners manual about this and have sent an email to Garmin but heard nothing back yet... Everything else works great... I checked the transducer if something was on it but there wasn't...

Re: Garmin 178c GPS / Sounder Indications?

When the unit does not get good bottom returns that is what it will do. This is usually a transducer problem or air under the transducer. Does it do this at trolling speeds or higher speeds? If at higher speeds then could be something on the boat infront of the transducer to create bubbles. Use liquid dish soap and a soft rag to clean oil off the transducer then flush with clean water. Make sure the transducer is tight not loose where can flop around or push up at speed. Make sure at least one half of the transducer is below the hull. On aluminum boats may need to be still further below the hull. Check that the transducer cable is clean and tight. Check the battery voltage to the unit. Try turning the sensitivity up and down and see if that helps.

Re: Garmin 178c GPS / Sounder Indications?

Boatist covered the things you can correct for, very well. If you see the same problem when returning to the exact same spot, especially if just drifting, it could be caused by something unique on the bottom. I am not sure how it is caused, but I just call them twilight zones. Most of the time, it has been very shallow rocky bottom, where I have seen this. There is one spot though, on the inlet of a lake, that just drives my units crazy. Jumps back and forth from 15' to 30'. Actual depth is 15 and the area that it happens in is about 20' in diameter. Had different boats and transducer types over the same area, always drifting, happens every time. All were with the same type of head unit. Unfortunatly, it is not clear water such that I could see what is freaking the units out!