Re: putting cd player in 86 bayliner
No, you will not be able to just "plug and play". You will have to wire it up yourself.
Your new CD player will have a red, yellow, black, blue, and speaker wires.
Yellow is for the constant power supply, hooked to the battery. I suggest adding an inline fuse.
Red is for a switched power supply, usually like an ignition switch. I wired mine into a toggle switch so I didn't have to have my gauges, and whatnot powered just to listen to the radio.
Black is your ground wire.
Blue is for an accessory like an amplifier.
Just follow the install instructions and you'll be fine.