STOP!!!!! Sam!
Do NOT run THHN AC wire in your boat or any automotive/marine application! That is all we, and Lowes, sells. It will not last and is an extreme safety hazard. Don't make me post pics of the burning boat again.
You need to run at least automtive rated wire, first and foremost. Insulation is different, as is the individual guages of the wires and "lay" of the spiral of those wires to make whatever guage. Skip is right, can't see a reason for 10 guage anywhere really.
I like the terminal block Idea. I really like the way it's done on my Pickle, on the stringer. Moo's kinda sux being on the engine though. Haven't looked into the weather packs, might not be a bad idea either, my only concern is any upgrades or changes, could be a lot more hassle.
Ray