depth finder installation

Where and how do you typically mount the transducer on an enclosed fiberglass kayak like the Old Town Vapor 12s,  off the back of the keel or underneath the boat along side the keel or somewhere else?

I mounted mine in a Dagger Axis 12.0 sit inside kayak using a magnetic mount from http://www.fishfindermounts.com/
If your kayak has a "V" hull or has a great deal of rocker, you may find it will not be practical to glue the transducer inside the hull.

There is a thread regarding this set up ongoing right now. See the Magnetic Transducer Mount Review http://www.northwestkayakanglers.com/index.php?topic=15026.msg166252;topicseen#new

Install it in another kayak.  Malibu kayaks have a special recess specially made for mounting a transducer.  No Mickey Mouseing!

Thanks for the info and ideas.

After trying it on the keel for a while I'm experimenting with the duct seal through the hull method. I take it in and out and the duct seal is quite sticky so I used a pvc fitting. Just put in a little water. I've been very happy with this method so far.
It's in a tandem sit in.

I just used marine goop and glued it to shoot through the hull.  Works great!

In my Vapor, I used a portable Hummingbird from my drift boat.  I wanted to be able to take the transducer out so that I could use it in my other boats, so I made a small well from foam weather proofing material.  Like Rev, I used Goop, but only to seal the foam to the hull.  With a few drops of water, the transducer would read through the hull with no problem and last all day.  I tried several locations in the Vapor, it was pretty easy to peel the Goop to try another location. Right behind the seat with the thinner hull in that location worked the best, the temp was even pretty accurate after a few minutes.