Humminbird says NOT to use silicon to goop transducer...

They say only use epoxy and that silicone degrades the signal too much...what gives? Is this true?

In this case...would it be better to use the transducer in a pvc pipe filled with water technique that others seem to be using?

I have to exchange my transom transducer for a hull mount model...sigh. 2 weeks for swap.

I used the epoxy that they sent with my friend Mike's transducer to glue mine in. Took 2 days to dry! Still haven't caught any damn fish though.

I would surmise that it is an issue with the density of silicone.  The more dense the adhesive and the thinner the adhesive layer, the better the signal transmission should be.  With that said, I have had my transducer temporarily siliconed to the inside of my hull for the last few fishing trips and no noticeable problems (using 3M marine silicone).

My adhesive of choice is marine goop for a "permanent" installation.  I know my Eagle manual recommended a specific type/brand of epoxy for mounting the transducer inside the hull but I cannot remember what it was.

I've used rodbuilding epoxy in the past and it softened up over time with chronic exposure to moisture on the inside of my hull.  (I've since switched to a different brand of rodbuilding epoxy too).

Erik

Silicone and goop are not the same thing.  Epoxy will provide the best bond, but you may not be able to ever remove the transducer without tearing a hole in the boat.  I have done numerous Humminbird units with goop and its always worked great.

My humminbird is soundly in place with Marine Goop.  It works great.

Only one minor issue -- I try not to store the boat inverted in really hot weather because goop can soften and the puck can come ever-so-slightly loose.

I've used silicone (aquarium cement) and had no problems.  I tried epoxy, but it doesn't stick well and is too stiff - it doesn't flex with the boat.  For a fiberglass boat, epoxy is the end-all solution, but in our boats the adhesive needs to be fairly flexible.