For give me!! On smaller boats like yours, general there is no distinction between house and starting wiring.
I started out with a 19 footer and worked my way up. What I have done to my boat is add a 2-way battery switch and than add a combiner.
http://www.yandina.com/c100InfoR3.htmNo matter which battery the switch is on, if there is a charge being put out by the engine the combiner will close and both batteries will be charging. Once that that charge voltage is gone the combiner will open, disconnecting the batteries. What I like to do, leave the slip on battery #1. As the engine is running both are being charged. Anchor, have fun!! Upon restarting, switch to #2, go home and again both are charging.
In doing it this way, you KNOW both batteries can start the engine on any given day. If you only use 1 battery alone for the house, you will never know if that battery can put out enough to start the engine.
What the ACR will not not do is allow you to switch to ether battery in starting. That is were a combiner (you can add a manual switch to the combiner so both batteries will start the engine) and a battery switch come into play