FishFinders and battery useage (any electrians here?)

2 different systems(on my kayak) and 2 radically different battery
lifespans.

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My old set-up:

Battery....Cabela's....12vdc..7.0Ah

Eagle FishEasy 2
Current Drain...................300 ma (lights off)
Output Power...................1500 watts (peak to peak)
187.5 watts (RMS)
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New system:

Battery........."Power Source" .....12VDC......7.5Ah


Garmin 160
Power
Usage.........10 watts max
Nominal.....12VDC @ 0.8 Amps

Performance
Sonar Power Output...........400 watts RMS
3200 watts peak to peak

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Now here is the symptoms. With my old setup the battery would last a long
while. I would guess 40 hours.
In my new setup, the battery lasts about 6 hours.

Above are all the specs I could find.
Are there any electrically minded folks here that could explain the
difference?
Is my new battery defective?

Thanks