GP1670F issue marking fish in deepwater

[KauaiOffshore]

Aloha all,
I currently run an older GP1670F paired with a 600w airmar thru-hull. It will mark the bottom from about 1000‘ feet and shallower and show fish at about 400‘ and shallower. My question is if there is anyway for it to show fish when I’m out at the buoys in several thousand feet of water. I’m obviously not looking to see the bottom out there with a 600w transducer, but the unit will never show fish in deeper water even when there are large schools of fish directly under the boat from 20‘ down to 200‘. After I pass the 500-600 foot depth the fishfinder half of the combo is basically useless, just a blank screen. Do I need to upgrade my unit or is there some setting I can adjust? Thanks!

 

[Kraken]

With a 600w transducer you are reaching maximum depth. You would need at least a 1kw transducer to see further down in the water column.

 

[KauaiOffshore]

I understand that completely. I’m not looking to see deeper, I’m just wondering why I can mark fish in the top 300‘ of water column when the bottom is 400‘ or shallower, but I’m unable to mark fish 50-200‘ beneath the boat when the bottom is deeper. I’m not interested in seeing the bottom after 400‘, but I want to be able to mark fish in the top 200‘ of water column regardless of depth, if that makes sense.

 

[FishTech]

@KauaiOffshore I would suggest trying the following:
1. Manual range set to the depth that you desire.
2. Manual GAIN. Turn it up until you get some noise on the screen. I run my fish finders with pretty high gain but it bothers people that want a clean screen. If you want like the noise, turn gain down until the noise goes away.
3. Turn off accu-fish and bottom discrimination as these features compress targets. It's especially detrimental to run them both at the same time.
4. If this still doesn't get you good echoes you can try to adjust the TVG. Start out by reducing it from the default of 3. TVG ensures that fish echoes of the same size fish remain consistent in size from the seafloor to the surface.
5. Turn off clutter and interference if you can.

Additionally you could have the transducer tested by a dealer that has a transducer tester to ensure that it is indeed still healthy.