electrical-drawing-pdfs-t127.htmlLook in there for drawings...and do some research on boat wiring in google.
Generally, electronics are run off a switch panel, and the panel is fed by the battery positive lead. You set up a negative bus terminal strip, and that goes back to the battery neg terminal. The main panel has a main fuse near the battery, and each load, including the stereo is individually switched and fused at the panel. If your stereo has a clock and memory, it will require an 'always on' lead from the battery or you'll lose station memory.
For now, if you want instant tunes and don't have a spare slot on your panel, wire it to the battery with a fuse of the proper size to protect the wiring.
AMP goes in the center console, away from spray and rain. Get a marine amp with conformal coated circuit boards or the salt air will kill it dead in no time.
Do speakers yourself. You can also buy a radio that has an IPod accessory hook-in and buy a wired remote control panel, so you can keep the radio, I pod and amp in the console, and just have a wired remote, about a 3" diam circle, to cut out for radio/Ipod controls.
Look into the Fusion brand of radios...or just buy some over the counter disposable 12v powered speakers and stuff to get your Ipod blasting on the boat. When they rot away, toss and replace.