Carib 14 inside-hull transducer problem

I've been having some trouble with my inside-hull transducer mounting in my Eddyline Caribbean 14, using the water well method that is practiced so widely among the experts on this forum. 

First, my water well leaked during my April fishing trip, resulting in a steady reading of 0.6 feet on my FF.  Simple re-caulking couldn't stop the leak, so I removed everything and installed a quart-size round plastic container with the bottom cut out, epoxied to the hull just behind the front hatch on a flat area.  This one does not leak and holds plenty of water, with a lid so I can practically flip upside down and still keep water in there. 

So last weekend on my Shaver Lake skunk-trip  (as usual ) it was working fine at first, for the first 1/2 hour or so.  Once I got out to deeper water, maybe 40 feet or so, it got intermittent and then went to 0.6 feet again.  So when I took a break from trolling I slid up, opened the hatch and checked the water level.  No problem, plenty of water.  So now what's the problem?  Couldn't think of any changes to make so I just put the lid back on and finished my skunking. 

When I got back close to my launch spot, maybe 20 feet depth or so, it started working again!  Seemed to measure depths that made sense all the way to shore.  So it's something else. 

Weak signal? Affected by too-deep conditions?  In my old Trident with the scupper mount, this same FF and transducer had no trouble measuring over 700 feet deep in Tahoe, so I don't get why it would be so bad now.

Any ideas, oh great and wise assembly of kayak rigging experts?  Thanks.

Andy

I use a Scotty transducer arm. Works great every time.

The epoxy/hull contact may be compromised.  having in-hull water cup is meant to have nothing but water between the transducer and the plastic of the boat.

May as well use the goop method and dispose of the water cup altogether. 

Eddyline is a diferent plastic than my OK's.  I used GOOP method for the first few yaks and it always worked well.

Clean the area to goop well wipe with alcohol.  Put the tube tip right onto the plastic bottom inside your boat and squeeze out the goop evenly.  Make a nice fat mound in front of the tube tip.  visually check.  No bubbles is a must otherwise the signal degrades or is wonky.

Press the transducler down into your Goop Pile swiveling three or four times to rid of any air bubbles

Put a brick on top of it and leave it for 24 hours.

This is a 'permanent' install but it works great or always has for me.

Otherwise, yeah, use a scotty arm.  But that introduces some extra paddling drag and is another thing to catch your line on while fishing.

Bushy