I have it's "big brother" to the FishMark 320 - SeaFinder 320DF $239 .00 1500'/4000watts (Dual Freq. /Higher Power)
I love it , it holds bottom flat out in my 16' Deep V with the 25HP Merc. thumpin' , marks fish very well , and although it has split-screen zoom , the resolution is great enough that in 40 fow , you really DON'T need the zoom , but it's there for awesome definition...
I'm sure that it would be great on the big lake too! http://www.eaglesonar.com/Products/Sonar/seafinder320df.htm
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