Zincs

[(Nobody You Know)]

I'm getting only about 5 mounths out of a set of zincs (1988 40' DC). I think I should be getting better than this. We relocated the boat to a temporary location in S.C. recently, and the problem persisted, so apparantly this is not a marina problem. A couple of years ago when I became concerned I had it tested by a surveyor with a background in electrolisis. He said the problem is not the boat. But it's begining to look like the problem may well be the onboard as we have been a transient lately.

Am I wrong to think that I should be getting more than 5 months out of a seto of zincs?

If not, anybody got an ideas what might be the primay culprit?

I have also heard that Hatteras is installing something on all new vessels to minimize this problem (but it's not a galvanic isolator)?

Thanks,
Capt'n Bill

 

[Genesis]

Check for DC leakage and bonding system integrity.

Start by turning off EVERYTHING. Disconnect any "soft button" electronics (those without hard-wired power switches, e.g. chartplotters, etc)

Turn off all breakers and disconnect the batteries.

Connect a VOM across the battery leads, set to ohms. It should read infinite.

Turn on your DC breakers one at a time. When you find one that makes the meter read something, chase it down and find out why. If you find a soft-power-switch item, disconnect it and keep going. If not, you have something leaking current somewhere. Common items that do this include bilge pump switches.

If you get to "all circuits on" and still have an infiniite reading, then the problem is not on the DC side per-se.

Now verify all bonding connections. With the meter set to "Ohms" check from EACH bonded item (all seacocks, etc) back to the bonding strips along the hull. All must read less than 1 ohm (lower is better; a good connection is under 0.1 ohm.) Check the bonding system to DC negative (it'd be nice if they were separate, but its almost impossible to do since the engines are connected to DC negative.) If you find any bad bonding connections fix them.

Now do the same on the AC side, but BE CAREFUL TO MAKE DARN SURE ALL AC FEEDS ARE OFF FIRST! Note that it is HIGHLY unlikely that the AC side is responsible for this.

If you go through all of this and find nothing suspicious, and you're not plugged into shore power (or either have an isolation transformer OR have eliminated that as a cause), then its just your boat and its characteristic galvanic difference between the metals connected to the bonding system, and there's not much you can do about it other than to increase the size (not the surface area though) of the zincs so they last longer.

 

[luckydave215]

Mine only last a couple of months. Everything checks out OK, and I have an active system as well. My last boat (sail, and in the same marina) used zincs at about the same rate. It must be the location, water chemistry, etc.
btw The marina was completely rebuilt, docks, electrical, the works between the sale of my last boat and the purchase of this one.

 

[67hat34c]

My research indicates that if your boat is underzinced then the boats around yours will eat yours up.

Try using a guppy

 

[34Hatt]

The Quality of the zinc itself has is a factor also a local shop here http://www.propfixer.com/ makes there own and have been for many many years and theirs do last longer. There is a pdf about zincs on their web page.

 

[(Nobody You Know)]

Thanks all who have responded to my thread. It makes sense to attempt to run down any onboard problems before considering the type (or quantity) of zincs, and fault the marina as well. Genesis, I have my work cut out for me! Be interersting to see wht turns up (bilge pump wires immersed in water come to mind).

Capt'n Bill

 

[Genesis]

Yep.

A common problem is the pump SWITCH wires - the insulation gets compromised inside where you can't see it and of course those switches are often (usually?) immersed, at least in part......

 

[TedZ]

Galvanic isolators work fine and will stop you from cathodically protecting mother earth!

Ted

 

[Traveler 45C]

Karl, please put this thread in the FAQ section. I"m sure the procedure that you outlined will be needed from time to time in the future.

hmmm, how many times has this come up over the years?

 

[(Nobody You Know)]

Thanks Ted. Galvanic isolators have been considered in the past. I have a healthy fear of climbing aboard the swim platform after a swim and getting zapped upon touching any metal! This could easily happen to a diver as well (boat at the dock of course).

If after running down the (Genisis) check list I don't find anything, there is a transformer/isolator devise that I may consider. My boat's an '88 year model. My gut tells me it's an onboard problem that can be solved (the problem has persisted at other marinas). Just takes time - like everything else - away from cruisin!

Capt'n Bill

 

[Traveler 45C]

FWIW, mine and other boats in my marina were going through zincs at an unbelievable rate, I got close to maybe 3 months out of them and that's it. This all started after Hurr Ivan. When I complained to the marina management I was told that since there wasn't any current going through them they can't be the problem. My response was, "Well, they still shouldn't be hanging in the water, right?"

So I had my son tour all of the docks here and tie up all of the loose wires hanging in the water. That solved the problem.

 

[MikeP]

We get maybe 4-5 months out of 'em, that's about it. Our boat has isolation transformers but it doesn't get any better mileage on its zincs than did our old boat which had neither transformers nor a galvanic isloator.

 

[Traveler 45C]

Mike, were both of your boats in the same marina?

I'm thinking that you should get more than that out of them...

 

[MikeP]

Yep - Brittania here in Northport, NY!

 

[CapetaniosG]

If the boat is in the water, it is next to imposible to measure resistance due to the fact that the zincs and other underwater metals produce electric current. Testing bonding circuits should be done while the boat is in dry dock!

You could perform the various tests with the boat in the water but you need a silver/silver chloride cell and a millivolt meter. For more info on this refer to Nigel Calder's book "Boatowner's Mechanical and Electrical Manual" 3rd Edition pages 218 and 234.

CapetaniosG
Hatteras 53MY

 

[Traveler 45C]

Mike, perhaps it is due to a fault at your marina that both of your boats only got 4-5 months out of the zincs. I'm thinking that you should probably get more time out of them than that.

 

[yachtsmanbill]

IMHO-- As being new to owning a Hatt my first impression of the underwater running gear was, " what happened to the zincs?" That was answered by kneeling on the wet ground and grabbing a prop to turn I got 110 to the old bones. Definitely a leak on the a.c. system that needs to be found;PRONTO!
On my aluminum ROAMER here in Chicago, Ive been plagued with electrolysis problems for 20+ years and finally read Nigel Caulders book on corrosion on metal boats.He seemed like a blow hard but I read on--not so dumb after all !! After speaking with him he turned me on to YACHT CORROSION CONSULTANTS in
California. TMALSS ( to make a long story short ) nyuk nyuk, I bought their silver chloride HALF CELL and proceded with my readings. As things turned out I was putting about 6-10 volts into the water and my zincs were protecting the steel dock. SOLUTION: I needed about 125 lbs ( calculated ) of hull mounted zinc for protection.
That and an isolation transformer, rewiring with a 3 wire system
( ROAMER used 2 ) building a bonding system with shaft brushes and a product from YCC called a zinc saver brought my output down to around 10-15 MILLIVOLTS. IDEAL !! The zinc saver runs the a.c. ground to the bonding system AND to the shore supply. While running we determined that SHAFT ROTATION produced about 250MV ( 1/4 volt ) hence the shaft brushes.They also help prevent grounding through transmission bearings! I might add that the hot water heater had been wired reversed polarity--BAD! All was great until the city inspector condemned the electric at our yard. One season of wires hanging in the water ruined a 10 year old bottom job. Now if my neighbors s.p. cord is in the water I pull it up on the dock for BOTH of us. Google YCC and start reading and printing.You WILL be amazed. HATT TRICK

 

[Beckytek]

Capr'n bill, I have the same boat as you 88 40' DC. When the boat was hauled last year the zinc's on my shafts were completely gone. After checking the bonding system I found 3 no connections to both rudders and the front starboard strut. The connections were corroded at the connection. I presume this was my problem. You should have an isolation transformer already. My boat came with one, I'm sure yours is the same. Ron