Chasing m25xp smoke

[KWKloeber]

SD,

A zinc a couple times a year seems excessive.  Does the marina check periodically for stray current in their ground lines to try to locate offending boats?  it seems to me that there is a leakage issue there somewhere.  Have you checked yours for leakage? It shouldn;t be eaten up that quickly.  You will want to bond your Hx to a known good ground (if it's not already) to make sure it has the utmost protection against galvanic corrosion.

ken

[scgunner]

Ken,

I don't normally have to replace my HX zinc every 6 months, they usually last around 1 to 2 years, however there have been times when I've had to replace the zinc in two months or less, which is why I do a monthly check. I think if there was a problem with my boat the rapid burn rate of the zinc would be a lot more consistent. As far as the marina I'm in, the only thing they seem to be really good at is billing marina occupants. You're right,it shouldn't be eaten up that quickly, but sometimes, due to constantly changing conditions in the marina, it does.

[KWKloeber]

Kevin and SD.   Is your 12v negatives bonded to your shore power green ground?  IIWMB I'd check for stray current just for peace of mind.  I treat the zinc as a symptom and a last-chance firewall, not a solution.

[scgunner]

Ken,

In my case I doubt there's a problem with the shore power since my marina was completely rebuilt(wood docks to cement)a couple of years ago. Also since the burn rate on my zincs currently seems normal I don't see the need to go looking for a problem that's not really there. And I thought zincs were the solution---to galvanic corrosion. It's just a question of burn rate which goes to my original point to keep an eye on the zincs since the burn rate can be influenced by a number of factors besides just a bad ground.

[KWKloeber]

Kevin,

I took it that it was more variable so there might be an intermittent issue.. Certainly if you are happy with checking and using the zinc as the solution who's to second guess that.

-k


Just to clarify for others,

Understand that marina AC wiring doesn't cause galvanic corrosion (well normally anyway.)  It transmits the corrosion.
And brand new, perfect, marina wiring can exacerbate, not reduce that corrosion. 
In some situations, poor marina wiring could reduce the galvanic corrosion between boats.

Just because a Hx anode (zinc or magnesium or aluminum) corrodes rapidly (or if it lasts forever) doesn't necessarily reflect what's going on with the total picture.  Two different metals in an electrolyte (e.g., water) essentially create a DC battery.  The indication of the Hx anode can be completely separate (i.e., the Hx is sitting as a completely separate battery) from other metals on the boat that may galvanically corrode.  Or the Hx could be completely reflective of the overall situation.  It depends on what is, and is not, bonded.

Galvanic corrosion depends on an electrical connection -- non pffeding boat(s) can have an intermittent connection(s.) Or the offending boat(s) can have an intermittent connection(s.)  Or both could. 

-k

[sloopdog]

In regards to changing the HX zinc a couple times a year I'm sure it's a bit overkill.  The one I remove likely has a lot of life left in it but the replacement zincs that screw into the cap are cheap enough I like to just stay ahead of it and not risk losing one into the hx.  I'm still trying to get used to maintenance schedules out in the saltwater vs when I was on the fresh side of the locks down in Seattle.  Growth and saltwater seem to create some increased maintenance.

[Stu Jackson]

In regards to changing the HX zinc a couple times a year I'm sure it's a bit overkill.  The one I remove likely has a lot of life left in it but the replacement zincs that screw into the cap are cheap enough I like to just stay ahead of it and not risk losing one into the hx.  I'm still trying to get used to maintenance schedules out in the saltwater vs when I was on the fresh side of the locks down in Seattle.  Growth and saltwater seem to create some increased maintenance.

Good points.  Things DO change when you move your boat, even in saltwater to saltwater.  I used to have to change my zincs 4 times a year in California, same marina, same slip for 18 years, but the boats around me, except for my next door neighbor to starboard, changed regularly.  Once I moved here to BC, I have found 2 times a year works fine, same slip for 4+ years, neighbors change even more often, and the electrical "system" at my marina is kinda a joke. 

Just keep checking them and you'll find out what "your" schedule needs to be.

[Ron Hill]

Guys : Now that we have morphed off in to Zincs. 
If you are new to your C34 always check the depth that you Zn goes into the HX.  On my old engine I found that when I put a #2 pencils in to that hole that it would stop in about 2 1/2 inches.  The inside of the HX tubing stopped anything past that depth.  I had to cut off about 3/4" off a new Zn to make sure it would fit!!

Moral of the story is to check that depth needed with a pencil or screwdriver to make sure that you are not forcing a new Zn against the internal tubing. 

A thought

[scgunner]

The original HX that came on my boat didn't allow a full length zinc to be inserted, I also had to cut to fit. The replacement HX does allow for installation of a full length zinc. I think there was a design change down the road.

[Stu Jackson]

When I got both of my new 3 inch HXs, I took off the end caps to see what zincs would fit it, so I KNEW.  (In an earlier thread I discussed that I needed a second one because the bracket rubbed the first one and penetrated the shell.  My thread is in the 101 Topics under Good Guys - Sendure.)

[KWKloeber]

Here's OEM anode info that I had gathered over 25+ years (some p/ns and prices may have changed since I last checked them - I removed all the WM SKUs I had because they are all changed now.)

If your anode takes the following wrench, it tales the corresponding anode:

7/16" wrench   (see #1)
11/16" wrench (see #2)
9/16" wrench   (see #3)

Three caveats:
1) These are for the correct OEM Hx, if a different Hx is installed your mileage may vary.
2) If your end cap bolt is in the way - don't cut your anode just, 'er, get a shorter bolt.
3) These are old info, if anyone finds errors I will correct and wiki post it.

(#1)
***** 
M-25; 2" Hx
Anode length: 2", Dia 1/4" / 1/8" NPT - plug 1/4" UNC; 7/16" wrench for hex head
Zinc anode w/ plug
    Universal p/n 301069
    Canada Metal p/n CME00 / UPC: 10628309103191 / Substitute for Universal p/n 301069
Anode only, CMEZ00 / $2.99

(#2)
****
M3-20
M-25/ M-25XP; 3" Hx
Anode length: 1-1/4", Dia 1/2"; NPT: 3/8" - Plug 3/8" UNC / 11/16" wrench for hex head
Zinc anode w/ plug
   Universal p/n 301068
   Canada Metal p/n CME1F / Substitute for Universal p/n 301068
Anode only, CMEZ1F / $1.79

(#3)
****
M-25XPB; 3" Hx
Anode length: 1 3/4" Dia 3/8" 1/4" NPT - Plug 5/16" UNC / 9/16" wrench for hex head
Zinc anode w/ plug
   Westerbeke p/n 11885
   Canada Metal p/n CME0 / Substitute for Westerbeke # 11885
Anode only, CMEZ0 / $2.99

[Stu Jackson]

>>>>>>>>>>>

If your anode takes the following wrench, it tales the corresponding anode:

7/16" wrench   (see #1)
11/16" wrench (see #2)
9/16" wrench   (see #3)

>>>>>>>>>>>>>>>>>>>>>>>>>

>>>>>>>>>>>>>>>>>>>>>>>>>

Good summary.  However, I have found that my 11/16" nut can take two different sized zincs, a fat one and a skinny one.  Guess one size fits all doesn't necessarily apply.  I switched to a 3 inch HX years ago on my M25.  I use the skinny ones because I found that the fat ones, as they start disintegrating (as they should), are harder to remove from the hole.

[scgunner]

Stu,

I agree on the fat and skinny of the zincs, I use the fatty just because I like having more meat, even though you're right, it can be a bit of a pain extracting it. Also I'd avoid the Chinese zincs, they're poorly made and very hard to screw into the brass nut and all but impossible to get out so it's usually necessary to replace the whole unit.

[Jon W]

Check the threads on the zinc before using. I found the threads usually have excess material at the parting line from the casting process so they don't screw into the nut right. I use a small file to clean up the threads and they work fine.

[scgunner]

Or you can use American made zincs that just screw in finger tight and can be replaced almost as easily.