Breaker, Breaker 1-9 (actually 3-0)

 My inboard AC Shore power breaker (in the cockpit locker) was continuously tripping during the last few months.  Never would stay shut for more than a few hours, then trip.  

....Then I returned to the boat the following weekend with no shore power and crossed my fingers that the 6 year-old batteries were still good.

Using the principle of 'Occam's Razor', I attacked the problem 1 layer at a time, in order of fault probability:

1. Old Batteries (2016)- Replace them.  
2. Bad Battery Charger-  Monitor or replace it.   Battery charger is from circa 2005.
3. Bad AC Shore Power breaker.  Probably original equipment from 1987.
4. AC Grounds inboard.

#1 was pretty straightforward.  Went to West Marine and bought 2 batteries of the same form factor (Group 27).   $350 later and the breaker still tripped after a few hours :(    At least I have fresh batteries onboard now.

#2 was easy to check.  I bought an AC power 'snitch' from Amazon and plugged the Xantrex battery charger in to this socket.   The charger was only drawing 0.3 to 0.7 AC Amps, which should NOT be tripping what is supposed to be a 30 Amps AC feeder breaker:

#3.  Replace the AC breaker.  I bought the DPST Blue Sea Systems breaker from Defender.com and swapped it out. Of note, the breaker did not come with the 'tie bar' to gang the two poles together :(   Fortunately our friends at SD Marine Exchange had a tie bar available, along with some 10 gage wire lugs.  Breaker swap was straightforward, just took a while to replace the box and crimp lugs on to the AC wiring.

Here's the original breaker.  Was wired as single pole interrupt with a GFCI (which did not appear to be connected to the load side):

Here's the brand spanking new breaker after install.  Has held for 6 hours so far... will check on it in a week to see if my AC is still 'ON' in the boat:

Here's the look before I made all the connections... someone learned how to crimp!