navman fish 4500

[dog tooth]

hi guys
i have been having problems with a fish 4500 sounder
in shallow water (10m) its max speed to keep the bottom is about 9kn and it will keep the depth reading up to about 14kn.
The big problem is when i am using the sounder in deeper water from 60-130m. the boat has to be allmost stationary for the sounder to show accurate bottom structure.
i have tryed 50 and 200hz and this does not seem to help. i have also ajusted the gain but in deeper water the sonar is just not doing its job
i have also tryed changing the transducer angle.

Is this normal for sounders to strugle in deep water?
does anyone have any ideas how to fix this?

thinks
ivan

[Coontakinta]

never had mine in 60-130m but keeps good bottom def at near around 40kmh in 30-40m

[dog tooth]

thanks coontaknta
i guess i have some work to do

cheers