The Forum includes two threads on transducers: Transducer Installation and Transducer Location. Read both for a variety of ideas and useful tips.

The executive summary is that on the Marks I to IV, both go under the port-side forward dinette seat. There is no room under the sole forward of the keel and the sharp V-shape of the bow under the V-berth leaves no suitable place to install the transducers that would provide consistent flow to the knotmeter and a downward orientation for the depthsounder.

Cables should not pass through the bilge. Run them to the outboard, forward end of the locker. On some boats, it's possible to pass them up behind the panel on the outboard side of the dinette and into the shelf space above. If that's not possible, they can run forward through a hole in the main bulkhead and into the lower head locker. From the lower head locker, they then run upward through the upper head locker to the underside of the deck, then back through a hole in the main bulkhead, to run aft above the lip of the deckhead liner to the galley lockers. From there, the path is obvious. At no point should the cables be visible.