Garmin Sounder Loses Depth

[bigbruce]

I've got a Garmin 721 Chart/Sounder with an Airmar b60 through hull transducer. Worked fine last year, and I've updated the firmware. Just back from a trip to Tahsis and kept losing the bottom. It worked fine at low speed, but as soon as i got up on the step and into deep water, the depth reading would start to flash and not read properly. Once I stopped, it wouldn't read depth properly until I shut it off and restarted.
Any advice would be appreciated.

 

[Sangstercraft]

Not sure if there's a Hz setting you can select, but I switch between something like 80 and 200, and it makes a big difference. Worth experimenting with. Sounds like yours got reset to the factory settings perhaps.

 

[bigbruce]

Thanks, Sangstercraft, I'll give that a try. Mine is currently set to "auto".

 

[Charlie415]

When running at cruise I run at 200hz, which is a narrow beam angle. When fishing I use 50hz which is a wider beam angle therefore more coverage. BUT I do still see certain spots where my sounder looses bottom every time I pass over it.

 

[Sentinel]

Have you installed anything forward of your transducer on the hull like a water pickup that could be causing air bubbles.

 

[Old Blue]

My buddy had the same issue last week and it was in the settings, after playing around with the depth range we got it working. Same thing happened when he tried it again

 

[Kisinana]

I find mine when running in "auto" and at speed or quick changing depths will flip between my dual frequencies. It will do the same thing if at speed over a temperature inversion or even large schools of bait. It seems that when I stop it then stays at the lower frequency and will not lock the bottom until I literally stop moving. I have got in the habit of manual high frequency until I reach where I want to go and then hit auto.