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  • #18361

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    In an effort to not ignore the basics, I’m posting these tips on replacing zincs.

    The aftercooler and heat exchanger zinc cap threads are 1/2″npt and the gear cooler zincs caps are 3/8″npt.  Having taps of each size in your “zinc kit” is a good idea so you can chase those threads clean.  Thread the new pencils onto your caps and snug them up you do not want them coming lose and banging up the tube ends of your coolers, seen this too many times especially at the lower aftercooler cap.  Reinstall with pipe dope (Rectorseal 5 here).

    And as noted in an old post, do check your B series heat exchanger zinc length.  I (and others) have to cut them down to not hit the internal casting but some have reported no issue..

    Here’s some shots from this morning’s gear cooler zinc replacement.

    6 users thanked author for this post.
Viewing 19 replies - 1 through 19 (of 19 total)
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  • #130978

    Clark Leighs
    Participant

    I will chime in also. I Rectorseal #5  the zinc threads themselves.    Then I use pliers or a vise and a wrench to tighten the zinc into the cap.   Snug firmly only  as  the smaller ones can be weak and break if overtightened.

    Seals the threads so they are protected from  the seawater   so they do not degrade, at least not untill the rest of the zinc is gone.    That way they do not fall out of the cap.

    I  then rectorseal the cap threads  for the same reason, to prevent  those threads from degrading and stop leaks. Snug lightly so the threads on the cooler cap AND the zinc cap are metal to metal so there is an electrical connection.    TO be sure I will often use an ohmmeter as a double check.  The reading should be less than 1 ohm, down near zero ohms.

    Rob Schepis has done a nice job of an explanation.

    As far as hours of time  OR   calendar time  to pencil cooler  zincs changes     YOU must determine this.    Failure to do this job will result many times in zinc failure as they can often degrade faster than  you THINK.

    I did mine, with my new to me boat,  every month untill by observation I could see one zinc was good for 4-6 months,  the other much smaller one often needed a change in about 6 weeks.     Failure to do this determination will often result in a lack of zinc protection for an unacceptable length of time.

    Do your job and do not be lulled into thinking you can guess.    All boats will have their own zinc changing  cycle depending upon  salinity, hours of use, and many other factors.

    1 user thanked author for this post.
    #125201

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    hendoda, Your last sentence is key.  But there is always the risk of some stray current so try out the Mg anodes and see how they do.  Report back.

    #125180

    hendoda
    Participant

    Zinc or Magnesium for Fresh Water?

    What are your thoughts on using magnesium pencils in freshwater. Our 6CTA 8.3 has been in fresh water its entire life (2004). I pulled the pencil zincs and they were largely intact but coated with ‘sand’ which seemed like it would have prevented the zinc from being sacrificial. Not sure if they were ever changed, we purchased the boat in 2021. I now see that magnesium might be a better choice for freshwater. What are your thoughts? This doesn’t seem to be common so not sure if it’s necessary. Perhaps not much corrosion occurring in freshwater.

    #89856

    firehoser75
    Participant
    Engines: Cummins 6BTA M3-330 HP
    Location: Nanaimo, BC
    Country: Canada

    Also, I strongly suggest changing them out quite a while before they actually “need” replacement. On the scale of “boat costs” these zincs are relatively cheap. By changing them early, you avoid the mineral deposit issue causing them to stick inside, maybe requiring “fishing” the zinc out (hose removal etc.) and the dissolving of the zinc into small pieces that can partially block (or in the worst case block) the cooling passages, leading to overheats or the need for premature (off engine) servicing of the coolers.
    On my boat, that means changing them every 6 months.

    #89673

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Dumb question but how often hours wise should the zincs be replaced on the QSB 480 hp ? Thank you

    Mike

    “Zinc Life” is 100% dependent on the boat and it’s environment … things such as the type of water the zinc sits in at the dock, the “electro-environment” the boat is sitting in, the quality of the vessel’s bonding system, and the level of underprotection, protection or overprotection based on having the right amount of zinc. What you need to do is check them in a short interval, maybe 60 days or so and then go from there to establish your change out interval.

    #89658

    michael platzer
    Participant
    Vessel Name: Mikes Pride
    Engines: Cummins QSB 5.9
    Location: San Diego
    Country: United States

    How often do you replace zinc

    Dumb question but how often hours wise should the zincs be replaced on the QSB 480 hp ? Thank you

    Mike

    #31085

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Stephen Oliver wrote:

    Hi Rob
    First time seeing this post – so thanks…
    I too have had an issue with HX zinc lengths.. on one of the 2 engines – I thought it was crud build up as they are hard to get to on the SB engine without dislocating my wrists… . How much did you cut off? Half inch or so?
    Steve O

    Steve,
    Probably good timing that you brought this thread back to the top as it is that commissioning time of the year.
    Sounds about right as to the cutoffs, here’s some visuals.

    #31057

    Stephen Oliver
    Participant
    Vessel Name: Ascella
    Engines: 2x Cummins 330hp Diamond
    Location: Perth, Australia
    Country: Australia

    In an effort to not ignore the basics, I’m posting these tips on replacing zincs.

    The aftercooler and heat exchanger zinc cap threads are 1/2″npt and the gear cooler zincs caps are 3/8″npt. Having taps of each size in your “zinc kit” is a good idea so you can chase those threads clean. Thread the new pencils onto your caps and snug them up you do not want them coming lose and banging up the tube ends of your coolers, seen this too many times especially at the lower aftercooler cap. Reinstall with pipe dope (Rectorseal 5 here).

    And as noted in an old post, do check your B series heat exchanger zinc length. I (and others) have to cut them down to not hit the internal casting but some have reported no issue..

    Here’s some shots from this morning’s gear cooler zinc replacement.

    Hi Rob

    First time seeing this post – so thanks…

    I too have had an issue with HX zinc lengths.. on one of the 2 engines – I thought it was crud build up as they are hard to get to on the SB engine without dislocating my wrists… . How much did you cut off? Half inch or so?

    Steve O

    #30910

    ciscokid69
    Participant
    Vessel Name: Turn Point
    Engines: Cummins QSB 6.7
    Location: Anacortes

    After cooler zinc problem

    New owner. Checking zincs on QSB 6.7. The after cooler zincs are screwed into a round brass (?) sleeve pressed or embedded in after cooler cover. While trying to remove the zinc, the sleeve is slipping and as a result the zinc cap will not unscrew. Suggestions?

    #30904

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Exactly why I put this article together….to put this issue to bed.

    https://www.sbmar.com/articles/myths-using-pipe-dope-threads/

    2 users thanked author for this post.
    #30903

    Nicholas
    Participant
    Engines: 1200hp Man d28 v12
    Location: Cocoa Beach, Fl
    Country: USA

    ok thanks. my approach to keep them from leaking has been to torque the thing until i popped blood vessels in my forehead, then curse myself for doing that a couple months later when trying to remove them to change them out. Using a little thread sealant would be much preferable.

    #30896

    john
    Participant

    They want good contact and no insulating sealant hampering the connection. That being said I don’t want a dripping zinc either. Skip the first thread with the sealant and you will be fine. As far as zincs sticking in the hole clean the hole with a small wire brush. Removing all the deposits. Also If you wait to long to change the zincs causes them to stick also. Mineral deposits will weld them to the parts they are trying to protect. Change them sooner than later

    #30889

    Nicholas
    Participant
    Engines: 1200hp Man d28 v12
    Location: Cocoa Beach, Fl
    Country: USA

    pipe dope?

    Rob – I realize this is an older thread but figured some people might have the same question as me. I’ve always heard not to use dope on zinc threads. The cummins O&M manual for my engine (480CE) states: “Do not use TeflonTM tape or pipe sealant on the threads of the sacrificial zinc plugs. Use of any type of sealant will insulate the zinc anode and prevent a good ground.” Is the pipe dope you are recommending especially formulated for this application? Or am I misreading this note?

    #18730

    David R Flamer
    Participant
    Vessel Name: Tax Break
    Engines: QSB5.9 380
    Location: Marina del Rey/Channel Islands Harbor, CA

    Rob

    I like that idea. Most of these were not installed by me. I’ll be sure to make sure the pencil is tight to the cap, for sure.

    #18703

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Removing the pencil zinc

    Are you making them tight with pliers before installing?  Also, clean the crud from the hole before new zinc goes in.

    As far as removing the pencil zinc that has unscrewed from the cap – take a spare brass cap and grind off all of the threads (external threads) and get the O.D. down enough that it is a “slip fit” into the cooler threads.  Thread it onto that stubborn zinc and give it a few light taps and that pencil should free up and slide out.  Basically you made you’re own puller tool..

    #18694

    David R Flamer
    Participant
    Vessel Name: Tax Break
    Engines: QSB5.9 380
    Location: Marina del Rey/Channel Islands Harbor, CA

    Mine always get stuck in there

    When I go to replace my zincs it always seems that the pencil unscrews from the cap and sticks inside what ever cooler is being protected.  I find this true especially on the HX and trans coolers.

    Is there anything that can be done to retrieve them out short of removing the cooling system hoses (or HX end cap) and fishing everything out? 

    #18603

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Zinc Sizes

    David, Thanks for chiming in here.  Here’s the zinc size chart I grabbed from BoatZincs.com showing the different lengths as you noted.  Funny how the shorter zincs are more money, I guess it’s like the decaf vs. regular coffee thing…

    #18602

    David Hays
    Participant
    Vessel Name: Kinship
    Engines: Cummins QSB 5.9L-380
    Location: Pacific Northwest

    Thanks!

    Thank you Rob.  That is really helpful.  I really like the suggestion of using some taps to clean the threads.  I will add some to my kit.

    On my 2008 build QSB 5.9L 380 engine, the heat exchanger calls for 1 5/8″ anodes.  I believe it is Cummins part #3970463 which is an E-2C size pencil anode.  The E-2 size pencil anodes are for the aftercooler.

    E-2C anodes are pretty easy to find and save the trouble of taking a hacksaw to the E-2 pencil anodes.   Not sure if all of the QSB 5.9 aftercooler are the same or not.

     

    #18433

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Good Stuff………….

     

    Tony

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