interference in speakers

so this is how my set up is wired.
dual batteries linked in a series on position 1 of the Perko switch, single battery on position 2 of Perko. 1 of the dual batteries is for cranking the boat, the other runs lights and speakers. the grounds for the amps are grounded to the non cranking battery in the series. i have checked all the grounds going from the battery to the amps, as well as the ground going from the HU. every thing has been re-grounded and appears to be soild. when i turn the boat on (just the batterys) the speakers make a faint "pop pop pop" and when i try to turn the ignition over there is a pretty loud "whine." any thoughts on something i might have missed?