BCB will correct me butFfor the hydrowave I would just tap into any hot wire I could find up there with the trolling motor plate off to look for it.For a second graph I would just drop a wire snake and go straight back to the batteries and wire it directly to my starter battery to avoid electrical interference. Id either drop it via the hole the first unit is using or though the metal plate the tm plug is in.C.O.D. Jr. III