A friend has a garmin 320 fish finder on his boat. It does not pick up the bottom at more than 3-4kts and I could not determine any discernible features over a low relief live bottom area in 80ft on a recent trip. Which essentially led us to drive around pointlessly for hours bc we could mark any bottom. I adjusted the gain and tried both 50 and 200hz frequencys. Basically I am asking if anyone uses this finder successfully offshore primarily for bottom fishing. And any advice on transducer placement on the transom to increase reading at at least trolling speed. Or this hung outdated and under gunned for this application entirely.
how many watts is this unit? The transducer is probably a 1/4"to high. Run a straight edge along the hull and make sure the bottom of the trans. is about an 1/8" lower than the hull. keep the unit in 200hz in less than 200’
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PROUD YANKEE
Oyster Baron
NMFS = No More Fishing Season
“Back home we got a taxidermy man. He gonna have a heart attack when he see what I brung him”
I think 500watts is the standard for that unit but I’m not sure.
I’ve usd one out to 100’ without difficulty. Zoom is very helpful when bottom relief is low … 
If it’s a transom mount transducer, it has to be in a spot that is away from turbulence created by the motors and the hull or it won’t work well. Does your unit work any better when you’re drifting? If so, it could be transducer placement.
19ft. Carolina Skiff
w/115hp Yamaha 4stroke
27ft. Contender
w/twin 225hp Yamaha 4stroke
had the bottom 10ft in zoom as is typical practice on any other finder i have ever used, maybe we were just off the good area and there was literally nothing to see, which is certainly possible given the captains experience using his GPS.
the finder seemed to worked fine at 1-2kts and drifting or on anchor. so i think there was alot to do with transducer placement. thanks for everyones input.