Boat Wiring Project (UDATED)

Hello all, I'm going to document my boat wiring project(s) here on this thread. Back ground: the boat is a 2009 Mako 1801 CC with a 2009 Mercury Optimax 115. The overall plan is to; 1) clean up the wiring in the center console, it is a mess with wires hanging everywhere, 2) add a radio and some additional lighting, 3) add a house battery. Currently (not including the 24v trolling motor batteries), the boat has 1 battery. I want to add a second battery so that I have a house battery and a starting battery. I will be using the Blue Sea Mini Add A Battery System, you can see that here: Blue Sea System. I am not a wiring guru, I am very much an armature so anyone with suggestions I am all ears. I have most of the supplies I need, and have already started working on cleaning up the CC. So, if you have any tips or suggestions I'm all ears. Thanks!

Ok folks I'm getting started on this dual battery setup and I have some questions. Attached is the wiring diagram. My current setup has 1 battery positive that goes to a perko switch that is only off and on. Then from the switch there are two lines that leave, I assume one goes to the motor, and one to the center console (fuse box). One of these has a 20amp inline breaker/fuse (??) I think that one goes to the motor. Does this sound correct? Then on the ground, it goes in the passageway and I assume to the console to ground the fuse panel. I do not have the Negative bus bar shown in this diagram. Do I just get one and run all the grounds to it? What grounds the buss bar? Thanks.

You take a 10g or bigger black wire from the battery neutral to the main lug on the negative buss bar. Then run your accessory grounds to it.

So I can do that with both of the batteries?