Have 2 also
Our '83 H27 came with 2 batteries also. Both are in battery boxes located in the space beneath the quarter berth, oriented athwartship. To install, first lower the battery #1 through the access hatch, hook up the cables, put on the battery box cover, slide it back and secure with a web strap screwed to the hull liner. Then drop in the second battery, hook up the cables, then secure the cover.The selector switch is installed inside the battery storage compartment, forward of the batteries.Paul---s/v Dilemma