After installing the new cable I thought I was home free until about a month later the same thing happened. I started reading and asking questions and the consensus was that the fine strands of the SS cable were subject to natural electrolysis since Stainless Steel is actually an alloy and thus contains metals of different nobility. The fine strands of the SS cable apparently allow the electrolysis process to accelerate.
Since I had my original Kevlar cable made by West Marine, the newer Amsteel Blue Synthetic lines have come to market. And they have superior ratings over SS or Kevlar, so next time I'll probably switch to this material.
I hope this was helpful to anyone interested.
I edited the above post, click small blue arrowhead to read the whole thing.
James, regardless of the pros and cons of synthetic line, having two stainless steel cables part in a month is amazing, there must be something more going on. While I agree the small strands of the cable make galvanic corrosion easier (more surface area per unit of volume), I don't agree that being an alloy is the cause. Galvanic corrosion happens when two dissimilar metals touch or are connected electrically. In an alloy I believe the metals are blended, and since each strand should have the same content there should be no galvanic corrosion.
I was also concerned about stray electricity around my boat so I reported the issue to the marina management and they promptly had their electrician check out the area and found no problem.
This is where I'm a bit doubtful. The electrician may have been testing for 120V AC stray current, a dangerous condition that can happen. He may not have been testing for a very weak (1.5 volt or less) DC charge. In fact, I'm not sure if he wouldn't have to have the correct alloy probe to measure it since it is in effect a chemical battery which depends on the metals involved.
Further, it is possible that the currents are within your own boat. One month is just too fast! There must be a problem.
I agree that the whole science involved is not intuitive. Here is a link that gives a decent explanation and may help you to discover where the problem lies, before it finds something else to attack.
It's from a marine insurance company, they are motivated to reduce claims so the info is unbiased.