The Set up that I'm using on a thick, full fiberglass old I/O Mako is a Humminbird 383C Combo GPS/ Fishfinder with a Shoot thru the Hull XP-90-T Transducer. The plastic transducer is epoxy'd to the hull in front of the engine, low in the bilge where the vee is not very steep. Before it was permanatly mounted, I used "Plumber's Putty" to hold in different places to see how it worked before I settled on it's permenant location. Humminbird supplied the slow cure epoxy with the transducer for proper mounting with very good instructions and excellent results. The 383C Combo GPS/FF works great in all water conditions and speeds without a blackout when going fast (40mph). It is compact and fits nice on a small helm station. the Mounting Bracket is simple and lets you remove or install the unit fast without playing with wires. Give this set up a look before you end your search. You can get just the Fishfinder alone (but why?) for around $300 or the combo for $400 plus 60 bucks for the shoot thru the hull transducer. Go to the Humminbird Store and take a look: http://store.humminbird.com/humminbird-pro...od406540-1.html http://store.humminbird.com/humminbird-pro...od710164-1.html