Coach not trying to hijack your thread but I have the same questions for a 1989 champion.Bass pro installed my 73sv transducer and it has been hit and miss or image clarity at low speeds and will not work on plane above 18mph. Curious if they possible chose a bad location.
Thump, getting 2D readings on plane with a transom-mount xducer is always trial and error. If 2D readings at speed are a priority, I always recommend an inhull xducer. With your 73sv, to have this option, you would need an adapter cable, inhull xducer, and a GT30 (xducer that came with unit won't work in this combo). If this is of interest, let me know if you have a CHIRP or nonCHIRP unit, and I can spec out the part numbers.
Otherwise, you need to adjust height and/or location, then run to check performance.