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Electrolysis.

jwolfgra

Member II
Hi Everyone - I've got a quick question on the wear rate on my zincs.

I recently moved my boat to a Marina in Alameda CA. I have a diver clean the hull every 3 months. In this months bill, he noted that the zinc was depleted and was replaced. This was after replacement of the zinc last service interval. In essence the shaft zinc needed to be replaced after 3 months. Does this seem like normal wear, or should I be suspicous of an electrolysis problem. Note - when not in use, my boat is completely powered down at the batter switch, and I do not have the 110 hooked up.

Any thoughts, thanks in advance.
 

Brisdon

Inactive Member
Sounds like your marina is a little hot. A shaft brush installed will help the prop and strut zinks last longer. I go one further and hang a zink fish over the side when ever my boat is in the marina. The zink in the drink really slows down the attack on the rest of the boat's metal.
 

Duncan

Member I
I too have a shaft brush, zinc in the drink, three 'beefy' shaft zincs and the zinc affixed to the end of the maxprop. My own 110 connection does not seem to affect the zincs, but who is doing what on the boats around me does. My zinc in the drink is about 1 X 4 X 10 inches in which I drilled a hole in the centre and inserted a piece of copper pipe and then put a bolt through. It cost about 15 dollars CDN and has lasted a year. The wire for the "drink zinc" connects inside the small "pocket" on the port side of my cockpit (E 34) so that when I pull up the wire and zinc the whole bit goes into a ziplock baggy and tucks into the "pocket." I also keep a very small wire brush in the baggy so that I can clean off the 'gunk' from the zinc. I am told that that gunk coating will reduce its effectiveness.
 

Sean Engle

Your Friendly Administrator
Administrator
Founder
Ever consider a plug?

Duncan -

On the 'zinc-in-the-drink' thing - have you ever considered this (this is what I'm thinking of doing). Make a dockside zinc that hangs from the dock, connected to a wire that runs to the boat (up the aft dockline, say...). Then it connects to a weather-proof connector on the after quarter. That connector runs directly to the engine block and/or the shaft itself.

I was thinking of this arrangement, as I'm getting ready to install removeable cockpit speakers which hang on the stern rail, and plug into weather-proof plugs back there. Then you don't have to worry about hauling the 'fish' aboard the boat...

Ideas - comments? :)

//sse
 

Duncan

Member I
Hi Sean: I too wondered about having to carry the "drink zinc" around with me until I went down to Port Townsend and stayed at Boat Haven Marina. We were sandwiched between plugged in live-aboards for three days. I was really glad to have my "drink zinc" available. The yacht club we belong to has reciprocal arrangements with a great number of other local clubs and you never know how 'hot' the next location will be. I guess it really depends on how you use your boat. If you had a dock mounted zinc it could be really big -- but would you pull it up and wire brush it off as much? Maybe it would be better because the wire to it could be really big. Those are my thoughts.
 

Duncan

Member I
Update
Wtih all my precautions, after just three months in the water, I have hauled out to have the bottom peeled (blisters) and found that all my zincs on the shaft and the one on the prop have been really attacked. Two of the beefy (squarish) shaft zincs had been subjected to electrosis so much that they were rattling around loose on the shaft. There is a boat permanently plugged in next to me and a live-aboard one over on the other side. Precautions be damned, if your spot in the marina is hot you just have to move.
 

Brisdon

Inactive Member
Duncan, is your "zink in the drink"tied into the bonding system with a good gauge of wire? I'm suprised that you are getting that much attack on the shaft zinc. If you suspect that a boat is shorting into the water, you can check it by putting a GFI between it and the dock source. If it keeps throwing, you know there are issues with that boat that are probably contributing to your problem. Typically it's a faulty water heater or a faulty battery charger left perpetually on. Also, do you have your 110 tied into your bonding, and if so is it through an isolator? Just checking.
 

Duncan

Member I
Thank you very much!
I am using number 8 AWG for the wire to the zink in the drink. When I checked out its connections I did find one loose. I will get after your other suggestions when I get back in the water (two months from now).
 

Tom Plummer

Member III
I think that I would be trying to find out who is leaking power into the water. If it is eating your zincs that quickly it could well be presenting a hazard to the diver. The diver will be fine as long as he stays in the water or if he does not become grounded when he exits the water but if he were to use a metal ladder he could get a nasty jolt.

We had a similar problem at a privately owned marina here locally. My dad owned a slip in the marina and in 4 months time he lost both of his brand new 22 inch props to electrolysis and he was not the only one who lost props and shafts. One boat sank when a thru hull went.

Here is how I located the offending boat. I put one lead of my Simson 260 in the water and hooked the other to the ground on our shore power outlet set the meter to read AC Volts. At our boat I was reading 72 VAC then I went up and down the dock turning on and off each boats shore power C/B while my dad watched the meter. When the voltage dropped off I had found the culprit, it was a commercial fishing boat and he had tied his neutral and his ground wire together and the taken that to his DC ground (the engine). I did this with the blessing of the condo owners association. Who took the owner of the boat to court for damages. He lost and had to pay for all of the damage he had caused.
 

Brisdon

Inactive Member
There's this strange tendency for boat owners in the US to tie their AC ground into the bonding system with their DC circuits. This is partly because boating associations and public agencies in the US still think it's 1945. It's kind of an old fashioned practice that protected boat owners from a 110 shock when they were hooked up to shore power before the invention of the GFI. The toll that this takes on the boat might once have been worth the safety of the people in contact with the boat when it's on shore power, but there are better ways to do this now. If you want to continue to tie the AC ground to the bonding system you can do it through a galvanic isolator. This item will let a large current through in an emergency but blocks small stray currents below about a volt. This costs a small amount but also does limited good. You can also use a paralleling transformer at the power supply so that the AC on the boat (although initiated by the AC at the dock) is completely isolated from the AC at the dock. It's just plain separate. It's like having the AC generated on the boat. This costs a lot more and does a lot more good. Both of these solutions predate the invention of cheap GFI's and I'm not sure anyone really gains anything by going with the more expensive routes. I don't have my AC tied to my bonding at all. What I do have is a GFI at the dock before the juice hits my boat. Because the GFI measures the power going out and the power comeing back to the dock, no current can go astray without tripping the circuit. If everyone with a boat in the water did one of these three things, we wouldn't have the galvanic problems that we all suffer. The problem is that most boats still have their AC bonded with their DC and no protection at all from faulty water heaters, cables in the bilge etc. Just makes ya fightin mad!
 

timoteo

Member II
electrolysis

hi there, anyone can tell me how i prevent electrolysis on my e29,
mean truhulls ect.....is it that i conect all of them with a green wire nr . 8 or 6 and as last go to the ground on my engine???
thanx for ur advice,
tim
 

rssailor

Moderator
bonding system

You need to run #8 green between all of your thru hulls, fuel tank (if metal), and the engine block. Connect all of the wires to a buss bar and then have one wire go to a zinc either the ones on the shaft, or one that hangs overboard at the slip. Also get a galvanic isolator that has a monitor on it. This check to see if you are getting galvanic current which is below .5 volts dc and is milliamps of current. You can compare voltage between the white wire and the green one. Anything above .5 volts is not good. Ryan
 

clohman

Member II
Another alternative: I have Marelon thru hulls and a rubber damper inserted in the propeller shaft coupler. My zincs haven't corroded in three years since there is no electrical conection to the water.
 

Geoff Johnson

Fellow Ericson Owner
I don't there has to be "an electrical connection with the water" (although it may increase electrolysis), since the prop and shaft are made of different metals.
 
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