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Serious Stray Current Corrosion, need advice

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    #16
    Stray current issues can be due either/both stray current between two different boats or two different parts of the same (your own) boat. In either case a current loop needs to be formed that goes through the water.

    (a) If the culprit is your own boat this requires that two separate metal parts of the boat are both in contact with the sea AND THE BONDING BETWEEN THEM IS BROKEN So, that the two metal parts can remain at slightly different voltage potential while the sea (water) completes the circuit between them. THIS CAN NOT BE REMEDIED using a galvanic isolator or an isolating transformer because the current does not flow through the Ground wire.
    (b) If the culprit is a nearby boat, current flows through the metal parts of the two boats and the water; In this case the common Ground node that each boat connects to with its own Ground wire completes the loop. This can be remedied using a galvanic isolator or isolation transformer; The isolation transformer solution is more expensive and may be more difficult to implement (size and weight of the transformer + where it should be located) but is considered a more complete/assured solution.

    You MUST find the culprit and fix it!

    Good luck.
    Retired, computer expert / executive
    Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
    Live in the Bay Area, CA, USA, boat in Turkey
    D-Marin @ Turgutreis in Bodrum/Turkey
    [email protected]
    [email protected]

    Comment


      #17
      Originally posted by MonteVista View Post
      Stray current issues can be due either/both stray current between two different boats or two different parts of the same (your own) boat. In either case a current loop needs to be formed that goes through the water.

      (a) If the culprit is your own boat this requires that two separate metal parts of the boat are both in contact with the sea AND THE BONDING BETWEEN THEM IS BROKEN So, that the two metal parts can remain at slightly different voltage potential while the sea (water) completes the circuit between them. THIS CAN NOT BE REMEDIED using a galvanic isolator or an isolating transformer because the current does not flow through the Ground wire.
      (b) If the culprit is a nearby boat, current flows through the metal parts of the two boats and the water; In this case the common Ground node that each boat connects to with its own Ground wire completes the loop. This can be remedied using a galvanic isolator or isolation transformer; The isolation transformer solution is more expensive and may be more difficult to implement (size and weight of the transformer + where it should be located) but is considered a more complete/assured solution.

      You MUST find the culprit and fix it!

      Good luck.
      Hmmm, can't say I agree with all that.

      If you ave a ground-neutral short in your boat then you will have a parallel current path for neutral current.
      This current will split between the neutral conductor and the seawater, flowing through the seawater, through the earth, then through the ground-neutral jumper in the marina pedestal making it’s way back to neutral.

      Perhas I’m missing something but I do not believe so. That said I am always open to ideas and explanations.

      Also...

      Based on the parallel path of current flow, we can see that a galvanic isolator will not rectify this problem.
      Where a galvanic isolator helps is when your boat is correct electrically, but your neighbors boat is not.
      In that scenario your neighbors parallel current path would be partially through seawater, to your boats metal parts, then through the ground conductor in your shore power cord, then through the ground-neutral jumper in the marina pedestal.
      In that case the galvanic isolator would help as it would block those stray currents because since there is a parallel current path the difference in potential would not be sufficient to pass current through the galvanic isolator which is in series with the boats ground block and the shore power conductor.


      KEVIN SANDERS
      4788 LISAS WAY - SEWARD ALASKA
      where are we right now​​​​​​???​

      https://share.findmespot.com/shared/...j23OquWOj2N3Xe

      Comment


        #18
        Kevin, we are splitting hairs! Sure, if there is a ground-to-neutral leak (presumably there is no short!) on your boat then current will be split between them and some might flow through the water, and the rest goes through the neutral on the pedestal before it comes back to your boat via the neutral wire. However, a boat's battery is NOT a current source; for there to be any current going through two metal parts and the water those metal parts must NOT be at the same potential. That is why I suggested that the bonding between them must be broken (at least poor/resistive connection). Also, if the current is split between two paths, the portion that goes through the water will be less, resulting in less damage.

        I still think (a) bonding is broken between two metal parts on the same boat, and/or (b) stray current is between two boats. If the issue is more pronounced on starboard side versus port I would check the bonding/negative cable and their connections between the two engines, if the boat has two engines.
        Retired, computer expert / executive
        Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
        Live in the Bay Area, CA, USA, boat in Turkey
        D-Marin @ Turgutreis in Bodrum/Turkey
        [email protected]
        [email protected]

        Comment


          #19
          One other thought occurred to me. I am not certain but I believe stray current corrosion is more damaging on the metal parts if those are at a more negative potential compared to the other part that is at a higher potential. If the culprit is a nearby boat, this suggests that a non-bounded metal part (i.e. higher potential) of that boat is touching the water while metal parts on the Cool_Beans boat may be properly bonded and grounded. Just a thought.
          Retired, computer expert / executive
          Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
          Live in the Bay Area, CA, USA, boat in Turkey
          D-Marin @ Turgutreis in Bodrum/Turkey
          [email protected]
          [email protected]

          Comment


            #20
            Originally posted by MonteVista View Post
            Kevin, we are splitting hairs! Sure, if there is a ground-to-neutral leak (presumably there is no short!) on your boat then current will be split between them and some might flow through the water, and the rest goes through the neutral on the pedestal before it comes back to your boat via the neutral wire. However, a boat's battery is NOT a current source; for there to be any current going through two metal parts and the water those metal parts must NOT be at the same potential. That is why I suggested that the bonding between them must be broken (at least poor/resistive connection). Also, if the current is split between two paths, the portion that goes through the water will less, resulting in less damage.

            I still think (a) bonding is broken between two metal parts on the same boat, and/or (b) stray current is between two boats. If the issue is more pronounced on starboard side versus port I would check the bonding/negative cable and their connections between the two engines, if the boat has two engines.
            Actually I think i figured it out.

            You are I think referencing DC current corrosion, and I am describing AC current induced corrosion.

            Happy happy

            KEVIN SANDERS
            4788 LISAS WAY - SEWARD ALASKA
            where are we right now​​​​​​???​

            https://share.findmespot.com/shared/...j23OquWOj2N3Xe

            Comment


              #21
              Dave
              Edmonds, WA
              "THE FIX"
              '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
              (.030 over-Vortec top end-part closed cooled)
              The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
              Misc. projects thread
              https://www.baylinerownersclub.org/f...56-gctid789773

              Comment


                #22
                Stray Current Test
                https://www.powerandmotoryacht.com/u...y-current-test

                Guntar
                1999 3988
                Cummins 270s

                Comment


                  #23
                  When bonding in the aft below deck for the under water metal, all under water metal should be bonded and tied together on both ends and tied to the transom zinc from both sides.
                  This includes a shaft wipe on both shafts.
                  Pat says: DO-IT-RIGHT THE FIRST TIME!

                  Bayliner 3870 "ALASKA33)
                  Twin 350 GM power
                  Located in Seward, AK
                  Retired marine surveyor

                  Comment


                    #24
                    I'm not as electrically fluent as many of the other posters in this thread but my 3870 seems to burn through zincs much faster than I would like. I recently discovered that my galvanic isolator was wired completely wrong in the factory and I suspect all of them were. I don't understand why so much corrosion would be occurring on your parts with zincs still attached so please update this thread as you work through the problem. Sorry for your loss, I replaced two prop shafts and two trim tabs last summer due to corrosion damage, don't want to go there again but still not sure how well protected I am.

                    Comment


                    • MacPhid
                      MacPhid commented
                      Editing a comment
                      BryGuy, how did you determine your galvanic isolator was wired incorrectly from the factory? How have you rewired it?
                      James

                    #25
                    Originally posted by BryGuy View Post
                    I'm not as electrically fluent as many of the other posters in this thread but my 3870 seems to burn through zincs much faster than I would like. I recently discovered that my galvanic isolator was wired completely wrong in the factory and I suspect all of them were. I don't understand why so much corrosion would be occurring on your parts with zincs still attached so please update this thread as you work through the problem. Sorry for your loss, I replaced two prop shafts and two trim tabs last summer due to corrosion damage, don't want to go there again but still not sure how well protected I am.
                    I plan too! I have a phone number recommendation of a local marine electrical guru and have an inquiry into a local marine surveyor who has corrosion expertise. I'll will keep this thread updated I find things out. If any of this can benefit another owner, it's it worth it!
                    . . .It places the lotion in the Basket. . .and that basket happens to be in a 1987 Bayliner 3870 w/ Hino 175's

                    Comment


                      #26
                      Why not disconnect the galvanic isolator and have all the underwater metal including the shafts bonded with shaft wipes.
                      This is including the trim tabs.
                      I connected the trim tabs with high grade SS welding wire outside the boat and a through bolt to connect to the bonding system.
                      This is how I was taught at a marine surveying school and is how I have my 3870 bonded.
                      I have had no issues with galvanic corrosion.
                      My 3870 have also been complexly re-wired, 100%.
                      Pat says: DO-IT-RIGHT THE FIRST TIME!

                      Bayliner 3870 "ALASKA33)
                      Twin 350 GM power
                      Located in Seward, AK
                      Retired marine surveyor

                      Comment


                        #27
                        Originally posted by boatworkfl View Post
                        Why not disconnect the galvanic isolator and have all the underwater metal including the shafts bonded with shaft wipes.
                        Bad advise... the galvanic isolator is there for a reason. I am surprised that a surveyor school taught students to do this.
                        1999 3788, Cummins 270 "Freedom"
                        2013 Boston Whaler 130 SS
                        Anacortes, WA

                        Comment


                          #28
                          Cool Beans,
                          Where exactly is the galvanic isolator located in your boat? Mine is a 1986 and I don’t believe I have one. At least I have not seen it-
                          Gibraltar, Mi.
                          1986- 3870- Hino 175's
                          1988 26' Shamrock/ Diesel
                          14' Zodiac Bay Runner

                          Comment


                          • builderdude
                            builderdude commented
                            Editing a comment
                            Probably buried behind the AC panel

                          • Steadfast70
                            Steadfast70 commented
                            Editing a comment
                            Mine is under the AC fuse panel inside the dash. But, installed in 1987 and I have no idea if it is still functioning or how to test it?

                          #29
                          Our boat had pretty bad electrolysis on underwater metals. The PO got sick and let the boat sit in slip behind his house for 6 years. Fortunately the prepurchase survey identified much of the damage and we got an additional discount to repair.
                          I hired a ABYC electrician with a solid reputation in Alameda. His inspection found a failed bonding system. Bayliner used open lug terminals on all the bonding wires. Water got wicked up into the wire strands thru capillary action and corroded the wire. He instructed me to completely rewire the bonding system using marine #8 and closed lugs and heat shrink to seal the connections. He loaned me a good crimping tool. He also had me make each run back to a terminal block located near the transom. Then one connection to the transom zinc. No daisy chaining.
                          He came out to the boat after it was back in the slip and tested the system a couple of different ways. I recall one test was dipping a silver lead into the surrounding water and then testing to each component inside the boat. He said the rewired system tested perfect. All has been well for the last 5 years.
                          2000 4788 w Cummins 370's, underhulls, swim step hull extension
                          12' Rendova center console with 40HP Yamaha
                          MV Kia Orana
                          Currently Alameda CA

                          Comment


                          • Cool_Beans
                            Cool_Beans commented
                            Editing a comment
                            Excellent advice, thanks! I'm planning to redo the bonding system. I've pulling old thru hulls and the copper wire strands are turning to pink powder.

                          #30
                          Originally posted by Sunbird View Post
                          Cool Beans,
                          Where exactly is the galvanic isolator located in your boat? Mine is a 1986 and I don’t believe I have one. At least I have not seen it-
                          It's under the AC panel. It's called a "Zinc Saver" and is probably OEM 1987. How do I test it? Light green wire on the left goes to the ground buss bar. Heavy green on right goes to genny. I assume 2 of the wires coming off of it goes to the bonding system (one each side)?

                          . . .It places the lotion in the Basket. . .and that basket happens to be in a 1987 Bayliner 3870 w/ Hino 175's

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