Let's say that you were going
to install a VHF radio, a depth sounder, an AM/FM CD player, and a
chart plotter. Four items.

Lets not forget bilge pump(s), running lights, cabin lights, lighter
plug outlet, etc.

Most boats, even a small boat, will probably have at least eight
circuits, which should each have their own circuit breaker on the main
panel.

Let me start counting of what I have and what I want to add:
1. Motor starter
2. Bilge pump
3. Bow light
4. Light near the stern
5. Interior light for inside of the center console
6. 12-volt outlet (not sure what it is for?)
7. VHF radio
8. Depth sounder
9. GPS

Seem like I definitely need a big panel for all these stuff even
without a AM/FM radio.

Jay Chan