cordialdevil
02-20-2010, 12:56 PM
My exterior zincs, on the trim tabs, shafts, rudders, stern are wearing at a rate that requires replacement about every 7-8 months. Black Gold, a 1995 38' Open, is in the water behind my house here in South Florida. I suspect a stray current in the canal, origin unknown, as the zincs should last at least 12 months. So this past week my good friend and mechanic, Tom Ferland and I have installed galvanic isolators from Mercury Marine on both shore feeds. Each kit consists of an isolator, one monitor and a small display that flashes green (for good) or red, or a combination of both colors with an audible alarm, depending upon the state of the electrical supply. Each unit is positioned inboard of the power receptacle, in the engine room, so that it monitors the power supply before it reaches the distribution panel.
After installation, the isolator monitoring power line 1 flashed a green/red light combination and sounded the alarm while the isolator connected to line 2 displayed a solid green. While tracing the boat connections from the inlet to the panel, we discovered a small isolator already installed (by the factory?) tucked away out of sight behind the electrical panel, with ground wires from both power lines going into the unit and one ground wire going out to the distribution panel.
After removing this unit (disconnecting shore power lines first and reconnecting after), the audible alarm was silent. We are seeing a strong, steady green light now on both displays, although there is also a very faint red pulse on each. Talking to Mercury Marine customer support, there might be a small electrical bleed left somewhere on the distribution panel so we are working on tracing it. Even a small bleed can cause accelerated zinc decay. We think the previously installed isolator must have had a fault which caused the alarm from power line 1 and most likely have been the cause of the zinc failures. Once we have determined what is causing the bleed at the panel and are therefore confident there is no electrical leak from Black Gold, the next step will be to test the canal water for any stray current.
After installation, the isolator monitoring power line 1 flashed a green/red light combination and sounded the alarm while the isolator connected to line 2 displayed a solid green. While tracing the boat connections from the inlet to the panel, we discovered a small isolator already installed (by the factory?) tucked away out of sight behind the electrical panel, with ground wires from both power lines going into the unit and one ground wire going out to the distribution panel.
After removing this unit (disconnecting shore power lines first and reconnecting after), the audible alarm was silent. We are seeing a strong, steady green light now on both displays, although there is also a very faint red pulse on each. Talking to Mercury Marine customer support, there might be a small electrical bleed left somewhere on the distribution panel so we are working on tracing it. Even a small bleed can cause accelerated zinc decay. We think the previously installed isolator must have had a fault which caused the alarm from power line 1 and most likely have been the cause of the zinc failures. Once we have determined what is causing the bleed at the panel and are therefore confident there is no electrical leak from Black Gold, the next step will be to test the canal water for any stray current.