[Ed]

Strick-

I have a Garmin 188c GPS with Sounder and a Furuno FCV-600L on my boat. The Garmin was a transom mount and never really worked right, except when at rest. THe Furuno is a shoot through the hull bilge mount and works all the way up to WOT at 45mph.

I just exchanged the Garmin 'ducer for a shoot thru the hull puck and will be installing it shortly.

If I were you...I would get the the shoot thru the hull type 'ducer. When installed correctly, they work great.

The problem with transom mounts is.....a lot of interference from air bubbles from the engine, hull wash, and trim tabs. By the time you figured out the best position....you would have drilled about 5 sets of holes in your transom.