No, not using autodepth. (didn't even know it was an option)  I had set the range to 20 ft.  Seemed like most of the time the depth was accurate, except for when in water less than 5 ft deep. 
G

@CptSloppywood-
Noted.  Filling the void was more of a 'last ditch' option if my issue was related to air bubbles due to the transducer install.   I'll try to adjust sensitivity first.  Hopefully that takes care of the issue.
Need to figure out how I can get a couple of hours to throw the boat in the water and do some testing.  Maybe the marina in Petaluma?  Although the river is pretty shallow, it'd probably be better to test in deeper water. 
G

The depth reading on the sounder read 40-ish feet, the line counter on the read said my depth was around 80 feet.

A couple of pictures of my install:
Transducer tucked up in the recess in the hull bottom.



It sticks down just a hair- maybe 1/4" below the bottom, but still protected by the keel ridge.  Thinking about trying to fill the open space in the recess with foam or something, to try to prevent air bubbles from causing issues.



Not sure how to adjust sensitivity, but I can probably figure it out.  One thing worth noting- I had this unit installed in my boat this summer- absolutely no issues with false bottom readings or anything else.  Fresh water (Lake Sonoma), depths from 8ft down to 180 or more.  Just a nice clear image.  Trying to figure out why installing it in a kayak in salt water would cause issues.

Only one other thing, which I'm not convinced is the problem- I'm using one of those Humminbird battery kits- a little lead-acid battery, I think 7.4 Amp-hours.  I had the voltage displaying on the screen, the entire time it was 12.7V or higher.  Made sure battery was fully charged.  My buddy thinks the Hook 7 might be pulling more power than the battery can handle, I don't think that's the case, and I don't think that's why the funny readings.

G

Got any photos of your boat?  I'm still trying to figure out where the best place is to mount things.  So far I have plans to add a Starport up in front of the main storage area (where the TacklePod goes) using the stock inserts.  Probably put the fish finder there, and after that I've got nothing.  Of course I don't know what other gear I need.  Should probably use the search function, see if there's a kayak outfitting or needed gear thread.
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Thank you both for the kind words.  Looking forward to learning from the collective wisdom.
I really do love the looks of the 440- the color scheme is fantastic, and the features on the boat look very well thought out- the square compartment just forward of the seat has a well for a battery and under the blue plug is a recessed area for mounting a transducer.  Lots of storage, 6 rod holders and the two round hatches behind the seat can function as dry storage or as  bait wells- each well has a scupper in it, allowing sea water in to keep live bail alive.

@CptSloppywood- how do you like the Reload?  Not that I'm having regrets or anything, but I'm seriously considering taking advantage of my employer's return policy to trade the 440 on the Reload.  Mainly to get the TacklePod and the closed bow area.  I think there's a TacklePod available for the 440, but I haven't been able to confirm that. 

G