wiring stereo on boat

how to do proper wiring on boat with inboard engine with 2 batteries that have battery isolator + 1,2,both,off swich (2ch amp and 2 coax 6,5 speakes,hu and rca ) where do i connect power and ground wires?

Amplifier power wire to output of the battery switch. Amplifier ground to the negative terminal of either battery. Radio yellow wire to a constant 12v wire at the ignition switch or fuse panel. Radio red wire to a switched power source that goes off with the key or an accessory switch on the dash.

thx iaai ,can i not conect yellow bcouse dont listen radio just music from usb. Radio red wire to a switched power source that goes off with the key or an accessory switch- will this cause alternator noise ?

You will have to connect the yellow wire if you want to listen to anything. If you connect the yellow with the red to a wire that is controlled by the key or the switch, everytime you turn the key on you are going to have to reset the bass and treble of the radio. Connect the yellow wire to a constant power source. You should not have engine noise.