Feed to Positive Buss Bar

[Aquamaniac]

Ok...have likely a dumb question....wanting to clean up the wiring in my '73 17' Aquasport but confused about choosing appropriate breaker and wire gauge from common terminal in battery switch to positive buss. I have seen recommendations of 40A breaker. But then my understanding is it should be less than the smallest wire 'downstream'. Several of the components have fairly small gauge (18-22)wires....so would not the 40A be too much? If I am reading chart right, 18 is only 10A. Pretty basic circuits...navlight, anchor light, aerator, cockpit light, panel light, horn, and GPS/depth finder. Will wire 24V TM with third battery and its own 60A breaker.
Also what would be sensible gauge for feed wire to buss (both pos and neg). I was considering 10 or 12.
Appreciate any help. As it stands, everything is basically directly wired to battery...although fused at least!!!
Thanks 😎

[jerryh3]

The breaker protects the wire from the battery to the fuse panel.  The individual fuses will protect the wires from the panel.  For a simple setup, I'd probably run a 30A breaker and 8 AWG wire from the battery to the fuse panel.

[RickK]

^^ What he said.  The CB on the main line is to protect the main current carrying wire from all the conbined loads/draw at the main panel.  I have a 30A re-settable on my 230. I used 8 GA for the feed wire.

[Aquamaniac]

Thanks guys.! Just to clarify...I was running the feed to a simple positive buss bar, not a fuse block. Intended to then connect buss bar to the the dash switch panel, as well as the horn and GPS. The panel has fuse for each switch.....protecting each individual circuit's wire. So use 8AWG from battery to buss and 8AWG from buss to dash panel as well???  I suspect I might need to rewire the dash panel to neaten things up as well.
Tried to post a pic, but did not work. Will see if I can remember how..... 

[Aquamaniac]

Pics...

[Aquamaniac]

[Aquamaniac]

Seems like the daisey-chain positive wiring from fuse to fuse on the dash panel would be 16AWG though....and at risk. (????). Guess there are issues to contend with when trying to keep original rather than using nice new modern fused switch panel.

[Aquamaniac]

The more I ponder this, why wouldn't a 10AWG feed with 30A breaker to the buss, then 10AWG to the dash panel, then 14AWG daisey chain sections be fine?
10AWG 80A max, 14 AWG 35A max ....both protected by the 30A breaker. Or is the 14 too close to 30 to be safe? How much margin is recommended?

[RickK]

That will work too.  The heaviest from battery thru breaker to buss bar.  Then after that you can run lighter to whatever needs power. A lot of boat wire is 16ga.  Gregs marine wire is a good source for wire, connectors, heat shrink, etc.

[Aquamaniac]

Hey Rick,
The 16 AWG is what had me concerned in the first place....its max is less than the 30A breaker.
After the fuse...yes, but before (like in the daisey chain)  seemed to be a risk. In fact several wires to lights, etc appear to be less than 16.....but are fused at the dash panel.

[RickK]

The 30a CB protects the wire from the battery to the buss strip.  Each load should have a fuse and the wire should be sized for the load.  Most loads on a boat are pretty small. It will be pretty hard to have everything turned on and drawing more than 30A.  If you have radar , that's a different story.