Re: Electrolysis.
Need some advice. My boat stays in salt water for only 2 months every fall. Alpaha One Gen II. For the last couple years I had kept the battery charger plugged in to shore power. Cost me an outdrive. Electrolysis destroyed it. Replaced the unit with SES outdrive. This year Id like to put a solar charger- maintainer on battery. Question: Will I have the same disasterous results with a solar charger?
Most the time the boat being damaged by galvanic corrosion is caused by other boats and electrical connections (marina) around them. If your boat is maintained and well grounded, stray electrical currents from other boats, shore power connections will be drawn to yours. Hooking up more items which draw power only makes you more susceptible. If you were not connected to shore power there would be no galvanic corrosion because you would not be grounded. There are two ways to stop or diminish these stray currents. Your boat needs to produce sufficient apposing current to make your boat less appealing, so to speak. Galvanic isolators should be installed to isolate your boat from external ground. A GI is a device that is inserted, in series, into the green grounding wire (safety ground) of your shore power feed to help minimize stray direct current / DC from flowing into your vessel. While blocking stray DC current it also has to allow for the passage of AC fault current. Dissimilar metals cause corrosion as well, aluminum casings and stainless steel props. A stainless steel prop makes a boat more attractive to stray currents then aluminum prop. Your boat needs a Mercathode installed at the least if one is not already there. Installing a galvanic isolator would be next.
My boat is in fresh water at a well kept marina, has a bravo 3 drive and stainless steel props. Every year when I pulled the boat for storage and pulled the props my hub was being corroded. Every year I would clean and prep the hub, re-prime and paint the hub, and the next year find more corrosion. After research I obtained the Merc test probe and found I was not producing sufficient apposing current to stop the corrosion. The next year I installed an additional Mercathode and two anodes in the hull mounted on each side of the drive. With the additional Mercathode I was able to get the field up to where the corrosion stopped.
Field currents and tech spec is listed below.
http://www.boatfix.com/merc/Techbk/97/97hs7.pdf
Fresh Water Areas -
620 - 1180 Millivolts with Digital Meter
Salt, Polluted or Mineral Laden Water Areas:
750 - 1180 Millivolts with Digital Meter
In closing, either install more protection, or add another battery or two for the bilge pump and do not plug your boat into shorepower.
