[erebus]

I put a Garmin 74SV on my Sceptre last summer, skipped the transom mount and went with a thru-hull transducer instead.
Not a fan of the transom mounts. Seen too many ruined transoms, and too many transducers flopping around and broken off at the ramp.

If you do go transom mount you can go through the transom just close out the core with epoxy where the wire goes through.