Under the starboard settee
Hi John:
The lower front corner under the starboard settee, where the hull is solid. You can temporarily tape the transducer to a ziploc bag half full of water (also duct-taped to the hull) or use some toilet bowl ring wax at different locations until you find the location that works best for you.
The location should be as low in the hull as possible and far enough aft to ensure that it stays submerged and can detect an echo even when the boat is heeled or if it punches over the top of a wave. It also needs to be far enough forward so that it doesn't get an echo from the wing on the keel. Good luck.
Peter
H23 "Raven"