Here is something I wrote on another forum in response to a question, which I thought might be of interest to some here?

Grounding your kicker, why? Like IFL asked, is it charging your battery? If not, NO!
It pobably would do more harm than good and just sets you up more for potential Electrolysis.
Yea, this is a quote!
"In the old days, the technique of bonding everything together worked okay. In its defense, the "bond everything together" approach makes your boat less sensitive to electrolytic corrosion that can result from faulty wiring on your own boat. The problem is, the "bond everything" approach leaves your boat totally defenseless to wiring errors in nearby boats and nearby industry, that cause stray DC currents to run through the water.

Today the technique of bonding everything together would still work fine if your boat spent all of its time on the high seas, in remote anchorages, or in marinas that were wired perfectly and in which all of the nearby yachts were wired perfectly. Having underwater metal bonded together in crowded marina's today, however, is asking for expensive trouble. As outlined above, it is avoidable trouble. It is possible, with careful wiring and a few capacitors, to have the best of all worlds, good RF and lightning grounds, ABYC approved DC and AC grounds, and security against electrolytic corrosion caused by hot marinas."

The whole article is here: http://www.sailmail.com/grounds.htm

Black Box? I have a friend that will probably "sell" you his? As he never bothers to turn it on? Have you tested to see if you even have a problem? Most people don't! One of the best things you can do is... believe it or not... keep your zincs above 50 percent. I change my zincs prior to July 1 every year. I went almost 2 years once, as I didn't think they needed it... it took me 6 months to figure out why I wasn't catching fish? I couldn't catch a fish to save my life. Changed my zincs... wella, problem solved!

How To Measure the Natural Electrolysis Voltage on Your Boat
Yea, another quote!
"A voltmeter with a scale of zero to one volt will measure the natural electrolysis. Place the ground lead of the meter on the motor or the battery ground. Place the positive lead on the stainless steel downrigger cable while it is in the water. The downrigger must be unplugged. The voltage you measure on the volt meter is your boat’s natural electrolysis voltage. When the stainless steel downrigger cable is lowered into the water, the natural ionization between the cable and the boat creates a positive charge of 0.7 to 0.9 volts in saltwater and 0.3 to 0.6 volts in fresh water. This natural voltage is dependent upon salinity and mineral content of the water. Your actual voltage may vary. "

A positive is a good thing, if its not at least 0.7 the first thing you want to do is check, clean or change those zincs! After that if it isn't in that range you could have lot more of a problem than needing a black box!