I am having trouble intalling a new gps/fish finder in dash.   The trouble I am having is that I dont understand the fuse panel under my steering wheel.  Can anyone forward me to some helpful information 

Thanks,

What would you like to know? A fuse block usually has a heavy gauge wire that feeds it. Then they're smaller gauge wires, based on load and fuse size, that come off and feed your devices.

Usually, or at least on homes and vehicles, the negative wires go directly to the load.  You know, white to white if 110 volts etc.  I would certainly think boats would be the same.  All negative wires go to the load and positive wires (red)would be the switched wire or wires that go to the fuse panel, through a switch and then to the device or load such as a pump, depthfinder, or a light.  Try that.  Use a meter of course to check for 12 volts from the fuse panel to negative on the batt.  On a meter, red is positive and black is ground or common. 

Does your boat already have a fishfinder?If it does You may be able to trace the wires you need to hook the new one up.The instructions from the new one should tell you the maximum fuse size(very important) to use and perhaps even the minimum wire size.

If you cannot trace the wires then use a new fuse slot and tab to hook up the positive wire and and the grounding tabs to hookup the negative wire.Any tab will due as will any free slot.