Anyone use a Humminbird 587 or 597 sonar/gps combo? Looking for something for the console of my little Champion Mean 16. Understand that it comes with a transom mount "skimmer" type transducer but that Humminbird has a transducer exchange program so that you can swap it for a "thru the hull" unit. How does this work? Is it done by the retailer?

How is the GPS accuracy on the 500 series?

Thanks,

Mark