Bonding system - Electrolysis

[POG]

I have to confess up front that electricity is not my strongest subject.  One thing is certain.  POG has somewhat of an electrolysis problem.  It seems focused on the propeller, the prop shaft and to some extent the strut.  A shaft sink will be eaten in about 4-5 months.  The small clamshell zinc I carry on the strut seems to disappear even faster.  Though the prop and the prop shaft are still serviceable they definitely do show electrolysis – leaching of the zinc leaves red patches where mostly copper remain.  Lately I have begun to use an extra, overboard zinc which I keep connected to the prop shaft in the bilge and to one of the inside strut bolts when the boat is at its berth.

The berth, which is a private dock I am renting, is somewhat under suspicion as its electrical wiring looks slightly less than confidence inspiring.

I look with bewilderment at POG's cruddy old bonding system and its green terminals and wonder what it is supposed to be doing – or may in fact be doing.   Is it working at all – and what about the three thru-hulls that have been replaced and are not connected to the bonding?

This is the first boat I own that sports a bonding system.  I suppose the theory behind it is that by connecting every metal part together you equalize their potential and stop current from flowing and causing electrolysis to a weaker item.   Or....  Anything else I should know about this technology?  Should I throw myself at the task of connecting the unconnected fittings, which seem just fine?

Then there is the issue of the ground for my 12V system.  Like in all other boats I have owned it is grounded on the  engine.  Is this the reason the prop and prop shaft get most of the electrolysis?  After all, they are a sort of extension of the egnine, through the gear box and the V drive, into the water.

Any advice from you refrigerator aficionados and electric wizards is most appreciated. 

[Bill]

Here is a link to an article that might help.   sailmail.com/grounds.htm    The biggest concern is what is around you, are there other private docks close by, if so they might be the problem with stray currents.  If you are at your boat regularly you could always disconnect your shorepower until you find the problem.  Also make sure your there is no DC ground wires connected to the AC ground or vice versa.  If you think your dock wiring is bad, check it out, it's worth your time and trouble to help the owner fix it.  My two cents worth, I'll sell you for a penny. 

Good Luck
Bill

[Bill]

Also another thought on your bonding system, don't get the bonding for lightning confused with the grounding of the DC system.  Most likely the thru hull wires are connected to the mast. 

Bill

[POG]

Thanks Bill.  Yes, the bonding wires are connected to the mast via the mast step.  I think I learned something from your comment about keeping the bonding separate from the 12V electrical ground, though I am not sure there is not a bonding wire bolted to the engine also on POG.  I will have to check.

And Dale....  I know you are lurking out there...  It may be over between us since I indicated that refrigeration is for sissies - but where are you when I need you?  I am certain you have all the answers to my initial questions.  HELP!

Carl

[Bill]

I hate to tell you but I have refrigeration also, but my wife who is a big sissy likes cold beer on the boat when we get there and skimpy bikini's, so what is a guy to do.  Tell her no cold beer.   

Bill

[Bill]

Sorry I posted my last post before I meant to,  you can get a galvonic isolator for 200 to $300.00.  Well worth the money vs replacing your shaft and prop. 

Can't wait for the weekend, its going to be in the high 70's, looking forward to some good sailing.

Bill

[POG]

What the heck is a galvanic isolator?  Even I might consider stooping to refrigeration to get on the right side of someone in a skimpy bikini.

Carl 

[Bill]

OK, I am don't understand electricity but here goes.  It is a magic little box that stops the low voltage stray current that causes electrolysis.  West Marine sells them and probably has a little write up online about them.  Its just magic.

Bill

[S/V Deo Volente]

Bill I love it! I've worked with electronics for 40+ years, and we some times say it's basically magic, it all works on smoke. when you let the smoke out it stops working.

[Dale Tanski]

I must apologize... I have been asleep at the switch on this thread.  Work, work, and more WORK!  I will be working this weekend as well.  

Fortunately I do not have or ever had an electrolysis problem on a boat.  Our cars here in Buffalo, NY are a different story, as all winter long we heap ton after ton of salt on our roads, all brought on by litigation due to unscrupulous lawyers and poor drivers.  A car in this area can turn to swiss cheese in but a few years.  

I must say that the article that Bill posted the link to in the beginning of this thread is excellent.  It really doesn't get much better than that.  As far as galvanic isolators go they are comprised of diodes that control the flow of stray current that is the root cause of most electrolysis.  A diode is nothing more than the electrical equivalent to a check valve in the water works business.  Something can flow one way but not the other.  It is a bit more technical than that but I like the magic and smoke theory.  I found this link that may be very usefull.

http://www.yandina.com/galvanicIsolator.htm

I must say that most electrolysis problems I have seen in fresh water have been primarily from the electrical system at the marina.  I have seen aluminum fishing boats shed their paint in a few short seasons.  Most boaters in sweet water haven't a clew what a sacrificial zinc is and what they do.  A boat in fresh water will retain the factory installed zinc for 20+ years.  As for the marina wiring issues, I have read about people that take a swim off of their boat in a marina and are electrocuted.  Even though the water in our basin is clear as a bell I would be very hesitant on heading over the side.

Carl, do you know if the electrolysis problem was a problem before you bought the boat?  Were the zincs all pitted out when you got her or has this problem started recently.  Did you change bottom paint? Add a SSB radio, with a Dyna plate? Are you on shore power? If you are at a dock are the docks conductive (the frame work) so the problem could be traveling down the docks?  Is there a new boat near you and this started after they arrived? Is your self steering windvane conductive to the water and did you "ground" it?

I think POG will survive even without cold beverages and bikini's however we need to do a bit of forensics first.

Dale

[POG]

I finally got around reading the excellent link that Bill provided.  Interesting to find out that the bonding our boats were provided with at great cost, as it was all the rage, is actually making them much more vulnerable to electrolysis when parked in a marina.

The electrolysis is not new on POG, but it is ongoing, with zincs disappearing too fast for my taste.  I don't have any boats in close proximity.  The nearest one is 50-60 yards away on another private dock.  I try not to leave shore power connected when I am not working on the boat.  Bit of a mystery.

Hopefully the problem will decrease once I get the boat out to sea.

What has me more in a knot after reading Bill's link is the issue of lightning proterction.  As it is now the mast is connected, of sorts, through the corroded bonding system to all the thru-hulls, which - I guess - would serve as your lightning ground.  I am not very happy about all of that...

Carl