Last weekend I installed both a fishfinder and a stereo (everything is
installed but I need to complete wiring to fuse block).

When I look at the fuse block, I saw that I still have 3 or 4 unused
spots. For both items, the positive wire, I believe, simply connects
to the male connector and above each of these connectors there is a
palce to insert the proper amp fuse (2A for fishfinder and 10A for
stereo). The part I am not sure is the ground wire.

I saw a bunch of yellow (ground??) cables all linked to a part of the
block with no fuses around. Is this sub-block a ground box? Is is
where I need to connect the ground (black) cable of the stereo as well
as the ground cable of the fishfinder?

Thanks as usual for your help! Andre