TOPIC: 48 hp tilt and trim

Hi i have a 48 hp evinrude spl with tilt and trim, there is a black wire that goes to each of the pistons, anyone know what the purpose of the wire is? also one of the pistons is extending but not retracting all of the way, what is the correct way to bleed the system. i have a seloc book but it doesn't show this type of tolt and trim. thanks in advance