HX Zinc breakdown rate?

[Jeff_McKinney]

(I already looked for info on this before posting and could not find anything helpful)

I'm in the upper Chesapeake bay. I just finished winterizing and pulled the HX zinc to see if it needed changing (Universal 35). It was about half gone, so I replaced it. The boat has only been in the water about 3 1/2 months (launched Aug 2005). It's normally on shore power to keep the batteries topped up (and a dehumidifier going now). I don't have any experience with this sort of thing, so am wondering if this rate of breakdown is excessive.

The marina owner says his shore power system seems to be OK. I have not had any electrical issues. Any suggestions or advice is appreciated.

[Stu Jackson]

Jeff

I have a scheduled checkout of our HX zinc every three months.  Half the time it doesn't need one, the other half it does.  If you at least check it every three months, then you can begin to get a feel for what works for you.  As far as I know, shorepower should NOT affect this HX zinc, since its only purpose in life is to avoid the corrosion from the seawater going through the HX.  The other zincs on your prop and strut are the ones that usually go if there is an issue with shorepower (i.e., incorrectly wired shorepower, an incorrectly wired neighbor's boat or yours).

[Ron Hill]

Jeff : My experience on the lower Chesapeake Bay (more saline than upper Bay), I get a year out of my heat exchanger Zn.  I put about 250/300 hrs on my engine /year. 
My engine is NOT grounded  (isolated by the flexible coupling).   

[Ron Hill]

Guy's : I almost forgot to point out an important phenomena. 
I've seen 2 DIFFERENT size diameter Zinc's in the 3 inch heat exchanger - one is 3/8" and the other is 1/2".  Both need to be cut to length, so my answer is for my 1/2" diameter Zn.   

[David Comando]

While on the topic of the HX zinc, I wonder if the use of anti-sieze compound placed on the threads of the zinc will inhibit the normal breakdown of the zinc. Just wondering.
Don't worry...I don't lose sleep over it.
Dave
Kindred Spirit #55

[Ron Hill]

David : You don't want to put anything on the threads of the Zn that you put in the threaded holder or on the hex head holder threads when you screw it into the heat exchanger.  You want an "uninhibited" metal to metal contact(best electrical contact) so that the Zn Does erode, rather than the copper/brass in the heat exchanger!!   

[Jeff_McKinney]

Stu: Although it'll be a bit of extra work, it sounds like your quarterly zinc check might be the way to go. If nothing else it's a chance to check the residue buildup. Do you pull the end plate off each time when you check your or just remove the zinc?

Ron: I did not have to trim the new one and it went in without any problem. I guess Universal pre-cuts theirs to the correct length (?).

[Stu Jackson]

If the zinc is in reasonably good shape (i.e., it hasn't DISAPPEARED) why pull the end caps off?  My engine's runnin' fine at 160.  When the temp starts going up on a regular basis, I'll take the whole thing off and clean it out.  Please remember, I'm the guy who changed from a 2 inch HX on our M25 (and removed and cleaned it yearly!!!!!!) to a satisfied 3 inch HX which is doin' just fine!  :)

Sometimes I think trimming zincs is an urban myth, but when I hear that it should be done from a known and trusted colleague, I'll buy it.  I think it's kinda: whatever works for you.  I've never had to trim my pencil zincs, many others have mentioned they have to do it all the time.

Don't put ANYTHING between the threads on the pencil zinc holder and the HX.  The idea is to ALLOW maximum contact.

[Ron Hill]

Jeff : I wouldn't check you pencil Zn quarterly, as you aren't in a salty area like Stu.  To be sure you could check it in mid summer and see the Zn status.  As I mentioned, I only replace mine every year and I doubt you'll run your engine as much as I do.
I wouldn't screw around with the end caps unless they are leaking or you broke off a Zn and need to get the broken piece out.

You're lucky that your pencil Zn went in with no modification.  Most of us have to put a #2 pencil in the hole to see how far up there's room before hitting the cooling tubes.  From my experience, if you stick in a Zn that's too long you won't damage the tubes.  What will happen is you'll break off the Zn at the base where it (narrows) screws into the holder and you won't know it!! until you unscrew the holder and discover the Zn broke off.  So I'd still use the #2 pencil check just to make sure that there's clearance.

To answer your question - Universal could be selling the correct length Zn?  The replacements sold by Boat US/West Marine are  cheaper, but are probably longer - about 2 inches in length.  Again there could be 2 sizes (diameters) for the HX on the M35 engines as there is for the M25XP ( both have the 3" HX).   

[Ron Hill]

Guys : A couple of years ago I came up with the same question that David did - "can I use anti-seize" on the Zn threads into the holder?  The reason that I had the question was that the old threaded (corroded) stub of a used Zn broke off in the threaded holder while I was removing it.  I had to use an "easy out" to clear the threaded hole for a new Zn.  I thought maybe Anti-seize might lube it so it wouldn't have broken off.

Today I was calling Permatex about the Anaerobic gasket maker (that I was using to reseal my Hurth transmission after replacing a leaky seal - but that's another story); so I thought I'd ask them about the conductivity of their anti-seize.
Permatex said the conductivity was good with the #81419 "silver" anti seize (aluminum) that most of us are familiar with, but their copper anti-seize #31163 would have better conductivity. The tech I was talking to was familiar with what a Zn does and why it's needed in brackish water.

So the answer to David's question is, Yes.  I might consider it to be better to have metal to metal contact, but it's your choice if you want to use Anti-seize or not!!!     

[willie]

Hi, I am new to all of this!

I have a 2005 c34, in portland on the Columbia river. What are you guy's talking about? HX zinc?

This sounds important...

[Ron Hill]

Willie : Yes, there's a pencil Zn in your heat exchanger (under side port) and it's IMPORTANT to protect the copper heat exchanger!!!  Read your engine manual and look in the engine pictures and they should show a Zn. 

[dave davis]

This is what can happen when you have strange currents running arrande. Don't ask me how?

[willie]

Thanks everyone.

http://marinesurvey.com/yacht/corrosion_1.htm

[Stu Jackson]

Jeff, (This is a compliation of some earlier posts I had made attempting to clarify and explain how the C34 website is arrranged; some have recently said that "There's TOO MUCH information," an not wholly unwarranted statement.  For newcomers, the best way to get around is to start reading and use the search engine on BOTH the message board and the separate search engine on the original homepage material.)

The original C34 web page (www.c34.org) has an FAQ section.  The following is posted there: http://www.c34.org/faq-pages/faq-heat-exchanger.html.  Note that these are BOAT related FAQs, and not "how to use the website" FAQs.

This message board is relatively "new" (compared to the long history of the C34 website) and is an ongoing resource for technical information in addition to the archived and captured boat technical information at www.c34.org, with it's own Projects, FAQs and Tech Notes (for C34IA members).  They Tech Notes Online are available ONLINE to C34IA members.  They also come on a FREE CD-ROM when you join the Association.

The index of all available Tech Notes is available to all:  http://www.c34.org/techindex_top.htm

Your sources of technical information on C34s are:

--  Original Webpage FAQs

--  This Message Board on the Forum

--  Original Webpage Tech Notes

--  Original Webpage Projects

These have all of the technical information that has been so graciously shared by C34 owners since 1987, all right here on your website.

Here's a brief history: The Original Home page www.c34.org and the associated Projects and FAQs (http://www.c34.org/projects/projects.html and http://www.c34.org/faq-pages/faq.html) were developed over the years to organize and collect the vast amount of information that had been generated by interested C34 owners about their boats.

The FAQs, particularly, were made by a handful of us who took our own personal time and copied material from the older email "List" and made "articles" about the subjects.  They were prepared and edited, then emailed to the Associate Webmasters, who then posted them on the website.  As noted to me recently, those FAQs are primarily concerned with Mark I boats, although some systems remain the same (i.e., HX zincs!)

With the advent of the searchable Message Board only a few years ago, there was no longer a need to do that time consuming work.  On the Message Board, the material is all there, on a central server and is searchable for any topic.  Phil has recently improved the search engine to allow it to work on more complicated search wording.