Depth Finder loses bottom when > 150'

[pcasterlin]

HI, I've got an e120 Classic (2), with DSM300. I think the transducer is the SS270, but may be the B258 or B260 (how do I tell?, The default in my setup is SS270). I've got all components updated to the latest software and boot versions.

The depth finder works great and is very good at finding bait and identifying fish and works for water temp. too. The problem is that once I get out past 150' or so deep, it stops finding the bottom. It intermittently gets readings up to about 200' and it will freeze at those for a few seconds, but ultimately just shows --.- for depth. I can manually adjust it and still identify targets in the water column down to about 150' but I don't get anything below that. After being out in deeper water and heading back in, it starts reading again in the low 200's intermittently and at 150' or so it begins working like it should again.

I've searched and searched and not found anyone with the same problem. I've tried software updates and playing with settings, but the behavior is consistent. It's expensive to test because I have to head 35 miles offshore to get to water deep enough.

Any suggestions?

Thanks,

Paul Casterlin