Sorry to 'jack this post but it seems like the perfect spot for my similar question...
I bought a Lowrance Mark 4 pro and bought a suction cup transom mount. I've tried various positions on the transom and angles, not to mention setting on the unit itself.
I've never achieved full fish archs, or it's loaded with surface clutter. I'm not sure if the unit is no good, if I'm placing it wrong, or if the the hull just isn't conducive to this. It's only 13 feet so it's hard to get the transducer far from the engine, plus there is a lot of drag on the fiberglass and pontoons from various patchwork.
anyone have advice or should I just return the unit and catch fish the old fashioned way?