Eagle Electronics SeaFinder 480DF - Manual (Page 16)

10
How low should you go?
For most situations, you should install your Skimmer transducer so
that its centerline is level with the bottom of the boat hull. This will
usually give you the best combination of smooth water flow and
protection from bangs and bumps.
Align transducer centerline with hull bottom.
However, there are times when you may need to adjust the transducer
slightly higher or lower. (The slots in the mounting brackets allow you
to loosen the screws and slide the transducer up or down.) If you
frequently lose bottom signal lock while running at high speed, the
transducer may be coming out of the water as you cross waves or
wakes. Move the transducer a little lower to help prevent this.
If you cruise or fish around lots of structure and cover, your transducer
may be frequently kicking up from object strikes. If you wish, you may
move the transducer a little higher for more protection.
There are two extremes you should avoid. Never let the edge of the
mounting bracket extend below the bottom of the hull. Never let the
bottom – the face – of the transducer rise above the bottom of the hull.
Shoot-thru-hull vs. Transom Mounting
Typically, shoot-thru-hull installations give excellent high speed
operation and good to excellent depth capability. There is no possibility
of damage from floating objects. It can't be knocked off when docking or
loading on the trailer.
Transom
Hull bottom
Transducer
centerline