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Thread: 8V71TI zincs

  1. #1

    8V71TI zincs

    Ok, PO painted everything white. So where are the zincs and how many on a 1972 8V71 TI?

    Water pump and heat exchanger, and where on each?

    Larry
    Seadation

  2. #2

    Re: 8V71TI zincs

    Two on the heat exchanger, one on each side. They will have a large bolt head - maybe around 1" or larger, I can't recall. One MIGHT be on the water pump but many people don't use one there since erosion causes a lot of zinc particles to end up in the intercoolers. There does not appear to be any issue with not having them in the pump. There have not been any in my 1980 54MY's water pumps since at least as far back as 1992 and the pumps are original.
    Mike P
    San Miguel de Allende, Mexico; Kent Island MD; San Antonio TX
    1980 53MY "Brigadoon"

  3. #3

    Re: 8V71TI zincs

    Quote Originally Posted by MikeP View Post
    Two on the heat exchanger, one on each side. They will have a large bolt head - maybe around 1" or larger, I can't recall. One MIGHT be on the water pump but many people don't use one there since erosion causes a lot of zinc particles to end up in the intercoolers. There does not appear to be any issue with not having them in the pump. There have not been any in my 1980 54MY's water pumps since at least as far back as 1992 and the pumps are original.

    I was told when we bought the boat not to put two zinks in the heat exchangers because they cause a battery effect with the exchanger in the middle(i dont know how to verify that but ive been doing it for 34 years). Ive always put one in the h2o pump because ive got it bonded to the fuel cooler.If you let them go too long its a pita getting them out of the cap
    "DON'T BELIEVE ANYTHING YOU READ OR HEAR AND ONLY HALF OF WHAT YOU SEE" - BEN FRANKLIN




    Endless Summer
    1967 50c 12/71n DDA 525hp
    ex Miss Betsy
    owners:
    Howard P. Miller 1967-1974
    Richard F Hull 1974-1976
    Robert J. & R.Scott Smith 1976-present

  4. #4

    Re: 8V71TI zincs

    Actually, I omitted the HE zinc that is first in the RW stream to avoid the erosion and zinc particles that end up in the HE. I did this for years. Last year I noticed some green corrosion around the HE connections and I thought it was possible that this was due to insufficient zincs so I put the "forward" zinc back in. However, I have since discovered that, as suggested by folks here, that the green is never caused by galvanic corrosion and was due to a very slight seepage from the RW gasket at the HE. So I have removed the forward zinc again. So the only zinc in my engines is the one on the exhaust end of the HE.
    Mike P
    San Miguel de Allende, Mexico; Kent Island MD; San Antonio TX
    1980 53MY "Brigadoon"

  5. #5

    Re: 8V71TI zincs

    Ive had a lot of trouble over the years with the 1/8 pipe plugs that drain the neat exc turning to mush usualy they look fine until u try to put a wrench on them. I had one blow out at sea and ruined the alternator. I never use teflon tape because it insulates the fittings. I always use permatex #2 on the threads and have only had a problem with these little plugs.their brass
    "DON'T BELIEVE ANYTHING YOU READ OR HEAR AND ONLY HALF OF WHAT YOU SEE" - BEN FRANKLIN




    Endless Summer
    1967 50c 12/71n DDA 525hp
    ex Miss Betsy
    owners:
    Howard P. Miller 1967-1974
    Richard F Hull 1974-1976
    Robert J. & R.Scott Smith 1976-present

  6. #6

    Re: 8V71TI zincs

    8V71TIs have zinc holes on both of the heat exchanger flanges. the flange can be placed so there is a zinc coming out the front side or the back side. Check both sides of both heat exchanger flanges for zinc caps. Original DD zinc caps have a square brass head. Newer universal replacement zinc caps have a brass hex head. These two types take different zincs because the threads on the original DD zincs were smaller.

    The water pump zinc is on the upper half of the raw water pump. It is a shorter zinc than the heat exchanger zincs. I keep zincs in the raw water pump and the heat exchanger outlet side. No matter where you put them, they can slough zinc shards into something, raw water pump into intercoolers, heat exchanger inlet into heat exchanger and heat exchanger outlet into the shower heads (raw water inlet to the exhaust), so I put them where they were originally designed to go.

    Doug

  7. Re: 8V71TI zincs

    "Ive always put one in the h2o pump because ive got it bonded to the fuel cooler."

    This is not standard on DD and I would recommend removing it. DD uses local pencil zincs. Keep in mind the only time any galvanic corrosion can take place is when water is present...that's often the only time even pencil zincs can function and that usually means the engine is running. For a few hundred engine run hours annualy, supplementary "bonding" wires can't do much good and likely offer the potential to introduce some unwanted current flows.

    When you remove any pencil zinc, if water does not flow out the opening, then the zinc is sitting in air...just falling apart and waiting to clog either the heat exchanger intake side or your shower heads in the exhaust dump.....

    No raw water when the engine iis off is typical on 8V71TI engine heat exchangers....although I've never figured out how the raw water dribbles out.....Like Mike, I removed my pressure side zinc on the heat exchanger for several years; Then I realized via discussions on this forum that unfortunately the outlet side zinc pieces will flow to the shower head....I finally decided on removing both pencil zincs keep the raw water system passages as clean as possible.

    It's easy to remove the inlet flange on your DD heatexchanger and look inside to be sure the core passages are open and free of zinc pieces...from time to time when replacing gaskets to get rid of green ooze crud I'd reach in and pull out mussel shell pieces....but mostly zinc debris..that's when I decided the zincs were more trouble than they were worth.

    As for the raw water pump zinc, I stopped replacing that as well ...Is it on the inlet or outlet side?? I foget..inlet side of the pump I think?? anyway, the rubber impeller isolates the zinc from either the raw water intake or the rest of the pump so it doesn't seem able to do much of anything....

    If you don't remove pencil zincs (not use them) then change them frequently before pieces corrode and fall off into your cooling system.
    Last edited by REBrueckner; 06-29-2010 at 09:42 AM.
    Rob Brueckner
    former 1972 48ft YF, 'Lazy Days'
    Boating isn't a matter of life and death: it's more important than that.

  8. #8

    Re: 8V71TI zincs

    Being new to 8v71 maintenance, I've reviewed all the threads on the engine Zincs issue. Is it true that every zinc on these engines is the same "pencil" zinc which screws into the cap/bolt head? Are these pencil zincs universal and can be bought at, say, West Marine, or do they have to be ordered from a DDA shop? Thanks

  9. #9

    Re: 8V71TI zincs

    As far as buying zinc, local hardware stores in boating areas often have zincs and usually MUCH cheaper than West Marine. Shaft zincs for our 53 (2") were $39 each at West last season; 19.95 at the hardware store. I don't remember the brand at west but the HW store zincs are Camp.

    As far as size - I have never used one in the water pump but, Nonchalant noted that the water pump zinc is shorter than the HE zincs. I'm back to no zincs anywhere in the engine. As mentioned, all the zincs are in the air when the engine is not running so they serve no purpose.

    Interestingly, our 16KW Northern Lights Genny does not have a place for a zinc fitting anywhere. Wonder why DD thought it was necessary when NL does not. Might just be "newer information" available since these DDs were made.
    Mike P
    San Miguel de Allende, Mexico; Kent Island MD; San Antonio TX
    1980 53MY "Brigadoon"

  10. #10

    Re: 8V71TI zincs

    Thanks, Mike. My concern is this: I opened one of the caps that the pencil zincs are fitted into and (of course) it was totally dissolved. However, the housing that this screwed into is turning a nice shade of blue/green (contrasts badly with the white DDA paint). So I figure the zincs had to be doing something?

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