Engine Zinc Question

I am about to change the zinc pencils on my Cat engines. Cat recommends coating the threads with Loctite Low Break Loose Pipe Sealant. Won't that interrupt the electrical contact between the zinc and the engine? I did use it last time I changed the zincs and the zincs did wear away. It just seems counter intuitive. Opinions please.

Thanks, Howard

Pipe threads cut through the stuff. I use rector seal. The sealant stops weeping along the threads.


Testing electrical continuity is easy using an ohm meter set at low level.

Interesting, I never thought of that. Makes sense. Thanks.

Would you mind posting a picture of what you're replacing. I looked at mine during de-winterization and they looked fairly complete, but I'm curious as to what one that needs to be replaced looks like.

Thanks!

Take a look at the zinc assembly. The part that screws in is not the zinc. For most engine anodes, you can get just replacement zinc and screw it into the old plug bolt.

Neverseize has various metals in its composition, the one I use for my aluminum boat is...aluminum-based.

clynn said:

Would you mind posting a picture of what you're replacing. I looked at mine during de-winterization and they looked fairly complete, but I'm curious as to what one that needs to be replaced looks like.

Thanks!

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Here is pic for you. I think you can tell the good one vs. the old.

Zinc holes are tapered thread as I recall. So if tightened properly they almost never leak. If you're worry about leakage and inhibiting electrical contact, just don't put sealant on the first few threads of the plug.

Am I correct that you should inspect your engine zincs every three months? And replace at 50% or more? Also is boatzincs.com the best source for zincs?

If in doubt, you can check the continuity with a digital multi meter from the cap/plug of the zinc to the engine after it has been installed.

boatzincs is an excellent source for engine zincs. For other types of zincs I prefer the quality of the Zimars sold by Deep Blue Yacht Supply, a great place for all your below the waterline needs, except bottom paint.

Pgitug said:

Am I correct that you should inspect your engine zincs every three months? And replace at 50% or more? Also is boatzincs.com the best source for zincs?

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I don't think there is a rule of thumb about how often to check zincs. I don't "check" mine, I just change them every 6 months. Zincs are inexpensive, so once I remove it to "check" it's just as easy to screw a new one back in. The photo I posted shows a badly worn zinc. Each of my engines have 5 zincs. All of the others came out looking almost new but I changed them anyway. I suspect the last time I changed them I must have missed changing the one in the picture.

I order all my zincs, engine, shafts etc. from boat zincs.com. Why? Mainly because they sell high quality---no Chinese junk. And, they are reasonably priced and my order usually comes the next day.

Howard

If you check you zincs every three months and replace those 50% wasted, then after a year or so you will develop an idea of which waste the fastest and need replacement more often.

Before I put in a fresh water flush system, I would change one zinc every three months, another every 6 months but the other three could go a year or more.

The conventional wisdom is to replace when 50% wasted. Non conductive scale builds up on them and that combined with less area results in greatly diminished performance at 50%.

And it doesn't matter whether you use a sealant or not. The threads will always bite through the sealant and make good contact with the female housing.

Finally, always screw down the pencil zinc into its brass plug tightly with a pair of pliers so it won't fall out in the engine housing when it wastes. But then you have to replace them timely, otherwise if it is too wasted the male end will break off when you try to unscrew it. I have tried drilling and an easy out and it just isn't worth it. Buy a new brass plug zinc when this happens.

You live with boats and you learn from boats ;-).

David

Greetings,
"I have tried drilling and an easy out and it just isn't worth it. " I agree but if one soaks the brass plug with the broken zinc stub in muriatic acid it (the zinc stub) will dissolve away. The usual safety concerns...safety glasses, rubber gloves, outside in the fresh air etc. As an aside, whenever I work with muriatic acid the FIRST thing I do is get a 2.5 gal pail filled with fresh water and have it standing by the work site.

hmason said:

I order all my zincs, engine, shafts etc. from boat zincs.com. Why? Mainly because they sell high quality---no Chinese junk. And, they are reasonably priced and my order usually comes the next day.

Howard

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Some of our boats were built in China, My Island Gypsy was built in Hong Kong--I don't consider her "junk". Where was yours built?

I do get your point---just trying to make mine.

Jealous of your GB---JohnP

We buy our replacement zinc pencils at the local marine supply store in our harbor. I write the date the zinc was changed on the holder cap with a Sharpie. We tend to change them every six or eight months but they are never deteriorated to the point of needing to be changed in that time. They're dirt cheap and we only need one per engine so we change them.

The only time we've ever gotten a faulty zinc anode it was one made in Canada. The Chinese make what they are hired to make by the company ordering it. More and more of our airplane components, including the entire vertical tail for the 737, are made in China. They do first class work if they are hired to do first class work.

Marin:

I think the Chinese can do excellent work when the design calls for it and someone is there to make sure they deliver to that design- ie Apple products or airframe parts. But when they produce something of their own at the cheapest price possible, the results aren't usually so good.

Poor quality zincs are simply a matter of metallurgy. Either the Chinese don't know what it takes or don't care as long they sell.

But Japan learned and so did Korea and Taiwan. China will ultimately figure it out.

David

I don't know where the zinc pencils sold in the marine supply store in our harbor are made. They're just in boxes sorted by size. But wherever they're made, they work just fine.

The Chinese have learned just a wee bit about boats in salt water over the last few thousand years so I suspect they have "figured out" zinc metallurgy by now.

Whether Estaban Funeman's Zinc and Storm Door company in Cleveland, Ohio buys the cheap zincs they sell through their mail order catalog from a Chinese manufacturer who cares about using correct metallurgy or not is another question.

Marin said:

The Chinese have learned just a wee bit about boats in salt water over the last few thousand years so I suspect they have "figured out" zinc metallurgy by now.

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Ah, but how long have they been making marine diesel engines?

But you are right, when Esteban buys his zincs from China, who knows what he will get. Esteban doesn't care. He just sells the cheapest thing he can buy. So the Chinese are quite right in selling him crap.

David

djmarchand said:

Ah, but how long have they been making marine diesel engines?

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Probably a lot longer than anyone in this country suspects. They make a very cool diesel outboard over there, for example, complete with a big exposed, belt-driven flywheel, that is the common mode of power on their smaller fishing boats.

Getting back to zincs, sealant is fine, but don't be tempted to use teflon tape as it will interfere with conductivity.

Since you guys are talking anodes, do you use shaft zincs with the copper crush contacts?
Do you even know what I'm talking about?
The reason I ask is that I sell Camp brand anodes that do have the contacts. The local divers don't buy them because they are not the cheapest available. If the copper contact isn't important to you guys, maybe I can switch to a less expensive brand.

HopCar said:

Since you guys are talking anodes, do you use shaft zincs with the copper crush contacts?
Do you even know what I'm talking about?
The reason I ask is that I sell Camp brand anodes that do have the contacts. The local divers don't buy them because they are not the cheapest available. If the copper contact isn't important to you guys, maybe I can switch to a less expensive brand.

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Yes I know what you're talking about. And yes I've used them.

I think that the crush contacts are an important feature and I would pay more to get them.

If you just bolt up a non contact egg anode, it may not make good contact with the shaft. The crush contact concentrates the force at one point so it makes good contact.

David

For the past two years I have been unable to get the shaft anodes with the copper contact. What I can get is an egg shaped anode with a hinge system that provides a larger surface of the zinc in contact with the shaft.\There is a difference. I haul once a year, not always at the same time. In the summers, I always get to dive and inspect. The copper crush kind have never, NEVER presented for a summer inspection. Last year was the first year with the hinge kind, and some zinc was still there for my next haulout, 14 months later. I won't be going back to the copper contact kind if I can control it.

Greetings,
Mr. K. Sounds like the crush type may have been doing it's job better than the hinge type.

koliver said:

For the past two years I have been unable to get the shaft anodes with the copper contact. What I can get is an egg shaped anode with a hinge system that provides a larger surface of the zinc in contact with the shaft.\There is a difference. I haul once a year, not always at the same time. In the summers, I always get to dive and inspect. The copper crush kind have never, NEVER presented for a summer inspection. Last year was the first year with the hinge kind, and some zinc was still there for my next haulout, 14 months later. I won't be going back to the copper contact kind if I can control it.

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if it is being dissolved, it is doing it's job. If it is still there after 14 months, it's not doing you any good. You might want to use a VOM to see what the voltage it reports.

Wouldn't zinc deterioration be related more to engine hours rather than calendar?


Jim
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Greetings,
Mr. JD. I think zinc depletion is a function of current density rather than time or engine use.

JDCAVE said:

Wouldn't zinc deterioration be related more to engine hours rather than calendar?

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A zinc is a sacrificial anode to balance the electrical potential of your boat. It is installed to let the free electrons eat on the zinc, rather than your boat's running gear and thru-hull fitting, etc.

Once the zinc is depleted (eaten away) the electrons go to work on your boat parts.

There are lots of things that cause zincs to be eaten away, boat hull material, salinity of the water, stray currents from bad electrical wiring (on both dock and boat), and flow of water over the surface of the boat. The faster you go, the higher electrical potential it builds and faster the anode will erode.

Best thing to do is test the electrical potential of your boat regularly using a silver/silver chloride reference electrode and a volt meter. You hook the reference cell to the volt meter positive lead and the ground lead to a known ground and see what the display reads. This is also a good way to test for stray currents in both your boat, other boats, or the dock power system.