Kevin Winchester from Hobie Sports is onto a winner with this little contraption, the 'bung to RAM adaptor' which has been fashioned to facilitate an external transducer installation for a Hobie kayak. An observant eye will figure it out immediately - the threaded end screws into the drain bung hole ( nicely positioned for a rear external transducer mount on most models) and the 1" rounded ball protrudes out a few inches. Any RAM 1" socket arm will clamp onto the ball, and various transducers could be mounted to various style of RAM bases. It's really just a matter of matching the base to the transducer install mounts. My mind has already started thinking about the possibility of mounting a camera from it!
Obviously, the advantage of having an external mounted transducer is that of achieving the clearest, most accurate reading possible. That's not always easy to do on a kayak, but this system certainly makes it easier. This little unit is available from Hobie Sports (and some other kayak dealers) for around AU$55 and comes in two styles - one that has a small cut-away inlet for wiring to be fed through and another without.