Much good information offered here. I also tend to go oversized on wiring, a little bit, just to make it a little more substantial. I always use tinned duplex wire and wired grounds also. Like was said, never use the hull as ground.
Another suggestion: Run one large duplex(10/2 red/black)cable from the battery terminals to the control/switch area. The large cable should terminate at a fuse panel(+)and a ground buss(-)right near the switches. Now each switch can be powered from the fuse panel and each ground can go back to the ground buss. This leaves your battery un-cluttered with only two sets of cables, one for the engine and one for all the boats equipment. Who wants a battery with a dozen wires all sticking out of it?
Wiring a bow light is frustrating sometimes figuring out where to run the wire. Hollow gunnels are a good place to run it. I used compressed air to blow a light string all the way through. Then I used the string to pull the wire through. Oarlock screws or bolts can get in the way of this sometimes.
Small battery boxes are a available for U1 and U1R sized battery. These batteries are powerful enough to start any 2cylinder engine and weigh only 20lbs. They are most popular for lawn tractors, perfect for a small light boat with lights, starter, and power-trim. Saves money buying it and gas every time out.