car cd player in boat

only 4???

you should have power and ground, at a minimum. if its wired to the Batt switch or a radio switch on the DC power panel, you'll have another wire. thats 2 or 3 for sure. now you have your speaker wires too. # of speakers x 2. some boats are wired with common ground systems but thats usually only on old boats with really old wires.

like i said, do the Switch test in my above post to see if it is hot wired directly to the battery, or the batt/DC panel switch. IF it STAYS on constantly, you either need to run a wire to the battery switch, which you hook up to the IGN wire on the radio. The CONSTANT on the radio goes to the 12V+ in the boat, and GROUND goes to GROUND.

If  you dont run the switched wire, the wires labled IGN and CONSTANT both get hooked to the 12V+ in the boat. you have to remember to always turn the radio with it this way as it'll drain the battery

The speaker wires are self explanitory i would think... + to +, - to -

what year make etc boat is this? that may help a little more in explaining this.....