I know what to do with that big hole your going to drill. I found an item at boaters world made by "Big John", I think. Can't remember the name but its white, about 2" in diameter. You drill a 1" hole in whatever surface and this thing fits in a covers it up. I've used one the one wire model for transducer cable and gps ant. cable, and the two wire model on the dash for the power and ducer cables for my 600l.
Went and found it after typeing that. Try this...
http://www.boatersworld.com/webapp/w...oductId=698718
Airslot