I got out to the boat today and took the camera so I got a picture of how I installed my transducer. I used the cap end of a pvc sewer pipe and epoxied it to the hull just off the centerline behind the battery. I cut a hole in the top of the screwed in piece, and then put a rubber battery post cover in the hole to seal it. The rubber piece has a slit in it so that the plug end of the transducer cable can be fed through it, and then it seals up around the wire to make it essentially watertight. Then I put a bead of silicone chalk on either side of the transducer and pressed it in place. There is still a gap on the bottom side of the transducer for water to flow under. I then put some water in the pipe and screwed the top on. It works just fine, and protects the transducer from things I have stored below the cockpit.
Dave
O'Day 222