Engine Zinc Question

Capt.Bill11 said:

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.

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True, they are called NPT, national pipe thread and are tapered to create a seal. Tightening distorts the threads on the brass plug and creates the seal. IMO they are designed for single use.
Reusing the plug again may not create the same distortion and seal. I little rector seal will help.

When changing engine zincs, it's good to chase the NPT threads with a tap to clean things up. A little sealant is a good idea. I've checked with an ohm meter and NEVER seen one insulated.

My engine zincs last between 6mo-1yr. Fortunately, only two. Some Cats are annoying with zincs everywhere.

I too use the shaft zinc and was dismayed by the lack of the copper balls. But after changing my shaft zinc a few times while diving, the ones without the balls are working just fine. Half or more eaten up at change. I do clean the shaft real well before mounting and also noticed that it has a real good grip on the shaft. I don't worry about the balls any more.

Rt and Stubones. I understand about the effect of the electrical potential on zincs, but all things being equal (I.e.electrical potential) a pencil zinc in a vessel in use should deteriorate faster than a zinc when the vessel isn't in use: 1) the concentration of zinc in within a heat exchanger has to be higher when the water inside is stagnant than when it is flowing, hastening deterioration; 2) the associated erosion from flowing water is higher than with stagnant water. I check my zincs more frequently in the summer when the vessel is in use than when it is sitting at the slip.


Jim
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I bought some pencil zincs for cummins 6.7. Been is service about 6 months so i thought i would check for wear. Not much wear but the new zincs came with new brass caps and the zincs are loosely threaded. Do i need to use lock tight on the pencil? Would hate for them to come loose and drop in the heat exchange.

I've never used lock tight or any thread sealant between the zinc and plug. Just give it a good twist by hand.

Remember, at some point in the future when that zinc is half as long and half as thick and somehow seemingly softer -- in order to replace it, you'll want to be able to unscrew it by hand without breaking it.

Ski in NC said:

I too use the shaft zinc and was dismayed by the lack of the copper balls. But after changing my shaft zinc a few times while diving, the ones without the balls are working just fine. Half or more eaten up at change. I do clean the shaft real well before mounting and also noticed that it has a real good grip on the shaft. I don't worry about the balls any more.

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Ski
Just wondering if you do a similar cleaning on the inside of the shaft zinc. I have started to us a small wire wheel in a drill to ensure the ID is clean and bright. Im in fresh water and use alum but procedure should be same for zinc.
Also assume you seat them well, but will mention it for others benefit. When tightening the zinc on the shaft I tighten it up and then fully seat the zinc using a hammer while rotating the shaft and retightening.
I do this all while on the hard before spring launch but wonder what those that change zincs in the water do?

Don,
That is the method described by Rod at marinehowto.com for installing anodes. He says clean attachment point(s) are necessary with a "solid" contact. He has a good article posted on his site.

firehoser75 said:

Don,
That is the method described by Rod at marinehowto.com for installing anodes. He says clean attachment point(s) are necessary with a "solid" contact. He has a good article posted on his site.

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Tom
Thanks CM is the best... go there often.
Don

For years I have cleaned the mounting areas FOR and OF ALL the zincs, shaft zincs, plate zincs, all zincs and so on. I then always check with my ohmmeter for continuity of less than 1 ohm, hopefully in the range of less than 0.5 ohm. Several times I have to dismount a zinc and reclean the zinc AND/OR the area it is mounted to.

I have seen zinc protection failure unless that is done and especially the ohm check.


Just fastening a zinc in place is NO guarantee it will actually work if the mounting surfaces are not adequately clean.

For pencil zincs I use a wrench to hold the cap and a pair of pliers to SNUG the anode into the cap. I no longer lose the zincs.

I then apply some sealant to the cap threads and check that. I realize that the water the anode is immersed may create a pathway to fool one but I have also checked when the raw water system was drained.

Every 6 months or so I then check for anode activity with my silver/silver cell and meter. I have caught a couple problems before they could cause damage.

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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They also figured out how to bulk up powdered milk with melamine.

My CAT 3208TAs have plastic end caps on the heat exchanger. The zincs thread into brass inserts that are molded into the plastic. Not sure how continuity is made through the plastic, but the zincs do deteriorate, so they are working.