When to change Zincs in Diesel engine

Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by Jeremygavin, Oct 16, 2018.

  1. Jeremygavin

    Jeremygavin Well-Known Member SILVER Sponsor

    Mar 6, 2012
    Cape Cod, MA
    2011 520 Sedan Bridge
    2016 Sea Ray 19 SPX OB
    2019 Walker Bay Generation 340
    Cummins QSM11s
    Mercury 150 Fourstroke
    Honda 40hp
    I am purchasing a 520 DB with Cummins QSM11s. These are my first marine Diesel engines but I have worked on Diesels before. I will be doing the winterization myself and have a good handle on the process so far. Do you change the zincs in the fall or wait till spring so you have full protection all season? I didn’t know if the antifreeze would effect them over the winter.
     
  2. CAMELLA

    CAMELLA Active Member SILVER Sponsor

    Dec 14, 2008
    Annapolis, Maryland
    2016 510 Fly
    Cummins QSM-11
    Congrats on the new boat, change them in the spring.
     
  3. bmac

    bmac Well-Known Member

    Jan 11, 2008
    Holbrook, NY
    2006 58 Sedan Bridge, Walker Bay Generation 390 RIB w/40hp Yamaha, 2014 Wellcraft 232 CC w/Yamaha
    MAN 900 CRM
    Agreed.
     
  4. The Bill Collector

    The Bill Collector Well-Known Member GOLD Sponsor

    Jun 2, 2008
    Tacoma, WA
    450 Sundancer
    3126 Cat's
    I don't winterize, but mine are changed every year when oils & filters are done.
     
  5. Jeremygavin

    Jeremygavin Well-Known Member SILVER Sponsor

    Mar 6, 2012
    Cape Cod, MA
    2011 520 Sedan Bridge
    2016 Sea Ray 19 SPX OB
    2019 Walker Bay Generation 340
    Cummins QSM11s
    Mercury 150 Fourstroke
    Honda 40hp
    Thanks for the replies.
     
  6. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    You change the anodes before they are needed!! Since the boat is new to you, I would at least look at them and make sure there is enough material left to do the job. If it hasn't been done in a while, they need to be done sooner than later. Anodes are cheap and easy to change.
     
  7. marks737

    marks737 Member

    268
    Sep 15, 2009
    NJ
    2005 390 Sundancer
    Cummins QSB 5.9
    I tried to remove one of my upper after cooler zincs but it's frozen and I can't budge it loose. The wrench started to round the nut corners. Any ideas on how to unfreeze so I can unscrew it?
     
  8. PMC

    PMC Well-Known Member

    Apr 10, 2009
    Long Island, NY
    2001 40 Sedan Bridge
    Cummins 6CTA
    It is a tapered thread, so once you get it to move it will free up. Try a 6 point socket over a wrench, it should go....otherwise it will be the advice of any stubborn bolt. Hammer, heat, etc. I dont think you'll need to go that far with a good socket.
     
  9. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    I tried all that in one of my coolers and I'm at the point where I need to remove the cooler, and drill and tap it out. Or worst case, I'm looking at having to replace the transmission cooler.
     
  10. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    There is more to this question than just the life of the anode. That is obvious.....replace them when they are 1/2 gone. However, at that point the anode is weakened and eroded to the point that you will probably snap the anode off the plug on 505 or more of your zincs. Recovering the lost anode from a cooler or heat exchanger is difficult and very time consuming if it is even possible.

    The other issue is that there is likely to be a lot of crud around the zinc that will bind the anode in the cooler or heat exchanger. When you unscrew the plug from the cooler or HE, you can also unscrew the anode from the plug. That leaves you trying to fish the anode out of the cooler or HE. More times than not, you end up pushing it into the cooler or HE where it is destined to remain until it is beat to pieces by the water flow or is cleaned out by an acid flush.

    I have found that it is far simpler to change the zincs early to avoid all the above. I "reload" my zincs so the cost is $1 to $3 for the anodes. Doubling my cost by changing the zincs every 6 month instead of every year may double my cost to $40 from $20, but if it saves me 2-4 hours diving for zinces, it is $$ well spent.

    Tricks to help: Use Teflon pipe dope on the plug threads. It seals and stops the metal to metal binding there the threads meet and makes removing the zince much easier.

    Use Loctite on the threads where the anode ecrews into the brass plug. Helps prevent the anode frpom unscrewing from the plug.
     
    techmitch likes this.
  11. JVM225

    JVM225 Well-Known Member GOLD Sponsor

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    Frank,
    The instructions from Cat for the zincs in my aftercooler advise to put the loctite on the shoulder of the Zinc. That loctite will seal the zinc to the stainless cap.
    I’ve got a complete extra set of caps and have been following your advice and changing them twice a year. It definitely makes the job better, but I still have some problems (less than before) with the steel caps either threading off the zinc leaving it in the aftercooler, or the zinc just snapping when I back the cap out causing the zinc to stay in place.
    Do you think it would be okay to loctite the threads on those zincs before screwing them in to the stainless caps?
    Not an engineer or anything, but I’m convinced the stainless caps and zinc rods are somehow a bad design. They’re the only ones that consistently give me problems.
     
    dtfeld likes this.
  12. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    John

    I used blue loctite on the threads and am assuming that I either have to chase the threads with a drill and tap or buy new heads along with the anodes. Some of the 1/4" pencil zincs would need to be changed about every 3 month to completely solve the problem. Additionally, the zinc material is easily cracked while manufacturing the thread or while seating to the head, and they are just disaster IMHO.

    To the OP, the advice here from Frank to do it sooner and more often is the best advice. You will get an idea of how long they will last after a couple changes.

    If you wait till spring, your expensive engine parts may become the anode if left unprotected.
     
  13. JVM225

    JVM225 Well-Known Member GOLD Sponsor

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    Dave, When the old zincs break off in the stainless caps I soak the caps in muriatic acid until the zincs remnants dissolve. Rinse the stainless caps and put new O rings on them and they are as good as new.
    I’ve got a complete extra set of the stainless caps so after I do the job on the boat I bring the ones I removed home to soak.
    I get the O rings from the local Cat Dealer for under a buck apiece, but I’m sure that if I searched around I could probably get the same size for much cheaper from Lowe’s or Home Depot.
    To help prevent the new ones from cracking when I install them, I try not to tighten them too much, relying instead on the O ring and “pipe dope” (I’ve actually been using Mercury Perfect Seal instead) on the cap’s stainless threads to seal.
    It’s still a nightmare of a job.
    I’ve got a bunch of extra brass caps for the other zincs too, but I rarely have a problem with those and the zincs that screw in to them.
    Not nearly as much trouble as the stupid stainless ones that go in the aftercooler.
     
    Last edited: Nov 16, 2018
  14. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    John. I read your technique..ingenious!! If I go back to salt water and zinc anodes, I'll be using that technique.

    However, I don't think the muratic acid treatment will work in my case as I have switched to aluminum (or aluminum alloy) anodes, so I'm stuck mechanically removing them with a drill and tap. The material is really soft and the right size drill in a cordless drill makes quick work of the bulk of the material, and a hand tap finished the job quickly. I can do all 22 of them in about 30 minutes. Finding the correct anodes is a whole other can of worms.

    Yeah, the CAT system sucks.
     
  15. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    Are you chasing the internal threads in the stainless caps with a tap before you insert the new anode? Any remnants of the old zinc in the cap will affect t he fit of the new one. Get a bottoming tap for the threads and try chasing them before you insert the new anode and see if that helps.

    The Stainless plugs have no give and the anodes have a bit of flash left between the trreads to insure t hat electrocal contact is made between the cap and anode. Be careful how tight you screw the anode into the cap.......I don't have a torque spec, but the idea is to get t hem tight enough to make electrical contact but not tight enough to crack the threaded part of the anode.

    And here is a tip: When removing the plug/cap from the aftercooler, first tighten the plug a wee bit. That uses the corrosion to hold the anode while it tightens the anode into the cap a bit while loosening the bond between the cap and the aftercooler. Then back the zinc out of the aftercooler.
     
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  16. techmitch

    techmitch Well-Known Member SILVER Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    A "bottoming" tap is key here
     
    JVM225 likes this.
  17. JVM225

    JVM225 Well-Known Member GOLD Sponsor

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    Thanks Frank! I’m going to get myself a 1/4 x 20 bottoming tap and give that a try.
    I do tighten the cap a bit before loosening it, hopefully it’s helping a little bit but I’m still averaging about a 50% problem rate with the aftercooler zincs.
    I think changing them more frequently has helped more than anything else.
     
  18. ttmott

    ttmott PhD in OCD GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    The anodes in the gear cooler on my last boat were the biggest problem; they broke off or came unthreaded about every time changed.
    I did a bit of experimenting - First I machined a solid brass 3/8" NPT plug with female 1/4-20 left hand threads for the zinc. Then bought some zinc stock and made several anodes with the left hand thread and reduced the anode diameter by .030". The problem went away.
     
    carterchapman and dtfeld like this.
  19. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    You, FW, and Quality Time - access to lathes! I'm envious...
     
    JVM225 likes this.
  20. Woody

    Woody Well-Known Member PLATINUM Sponsor

    Nov 20, 2007
    N. Wisconsin/Lk Superior
    2005 420DA
    Cummins 6CTA8.3
    If one of the problems is keeping the anode tight in the cap wouldn't an actual chaser be better to use than a tap?
     

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