Electrolysis issues

[MykeD]

I have a 2017 C24 that has major electrolysis issues (outdrive required major repairing, all of the zincs gone in weeks, and bow thruster required a replacement). We narrowed it down to the ACRs and took them out of line. Now we have issues with the batteries holding charge for any length of time. The batteries are new to this season. At the Newport RI boat show we noticed that the C24 now comes with an Galvanic Isolator. What changed? We have a spent a pretty penny fixing this only to stop the leakage but have a part working boat.

We don’t have a good history with power on this vessel. Our boat was delivered with a bad charger (Abso), bad batteries, and a bad windless each which took a while to diagnose.

What model isolator is being used? I can’t find it in the parts list. Could my ACRs be bad? What do the ACRs actually do on this boat. I get the concept but with a “Smart” charger, why are they needed?

My batteries now charge from shore power and from the alternator when over 1800(ish) RPMs but die soon after.


Sent from my iPhone using Tapatalk

 

[BB marine]

We narrowed it down to the ACRs and took them out of line.

I'm not sure how the ACR's could cause an issue with electrolysis. The ACR's are a connection between each positive battery bank. There is on small 14 gauge ground wire used to function the electronic switch. Your battery banks other than the engine battery will not charge without some type of connection to the engine battery. But you must isolate this connection when the engine is not running other wise it is just one big battery bank.


ACR's isolate each battery bank from one another when there is no charging source. When using a shore power charger with three out puts the ACR are really nor necessary. The battery banks can remain separated and charge properly. The ACR come into play when using the engine to charge the batteries. When the engine is started each bank is separate. Then the engine battery is charged by the engine alternator. When the engine battery is charged and reaches 13.0 volts for a few minutes the ACR closes and parallels the house and thruster batteries so all are being charged by the engine alternator. When the engine is shut off and the voltage drops below 12.7 Volts the ACR open and each bank is isolated again. Without the ACRs in service the house and thruster bank are not being charged from the engine and will be voltage depleted quickly if you are using 12V power.

The issue that is causing your anodes to be eroded quickly and the gear housing to be damaged is not likely caused from the ACR. It is caused from a shore power issue, a poorly wired dock, or a poorly wired boat next to your boat in the marina or your own pier. The other issue is how many anodes do you have to protect your lower unit and underwater hardware ? In a factory application probably not much. Just the engine anodes?? You may need to add more and there should be a Galvanic isolator installed in your boat to help protect your anodes from other boats using them. There is plenty of information on line to increase your knowledge as to what is causing the issue. In most cases it is not the boat it is where the boat is and how good the electrical system is that the boat is connected to. (shore power) and the boats connected to the shore power is normally the culprit.

 

[MykeD]

Thanks for explaining how the ACRs work. That is likely why we are seeing low voltage when not on shore power. I’ll put them back inline.

It is worth mentioning that we took the boat to multiple private docks and marinas to test and they all measured the same in terms of leakage when on shore power. We could disconnect and reconnect the ACR when on shore power and measure the leakage go and come in a multi-meter.

We had added a few anodes (outdrive, trim tabs, and bow thruster) to the boat and since added a few more but they were all being eaten in a very short period of time.

The person helping me just removed the ACRs from the boat to test them in isolation to see if turns anything up perhaps they are stuck in a position. Guessing here obviously.

I will look at an isolator. Not sure if the Fluid Motion guys can suggest one. Clearly these are on the new models for a reason.


Sent from my iPhone using Tapatalk

 

[Chimo]

I installed a ProMariner 30A galvanic Isolator. https://www.promariner.com/en/22034

It was an easy job and you can see photos in my album under Some Modifications. It increased the life of my anodes from about 4 months to my guess at 8 months. I change them when I lift the boat every 6 months in any case. I can't see any reason for the ACRs to have any effect at all.

 

[BB marine]

It is worth mentioning that we took the boat to multiple private docks and marinas to test and they all measured the same in terms of leakage when on shore power. We could disconnect and reconnect the ACR when on shore power and measure the leakage go and come in a multi-meter.

Leakage? I'm not sure what you are referring to. And how you are testing and where you are testing. Shore power testing at different marinas is confirming that your boats AC side is probably ok. In modern built boats there is a ELCI breaker installed that will trip if there is a faulty circuit that is "leaking" to ground. The Black (hot) and White (neutral) must have the same amount of current flowing through them. If there is an imbalance that means there is current going to the Green (ground) The ELCI will trip if this leakage is more than 30 milliamps (mA).

The issue you seem to be having is stray DC current. Stray DC current has a few ways to happen. The most common is through the shore power green ground. It doesn't take much. Your boat is fully bonded. ( It should be and that should be the first checks made. There should be continuity between every metal component in the water. There should be continuity between every anode and every metal component that is under water and bonded. A test from engine ground to every bonded component should show full continuity +/- 1 ohm.) The potential for DC stray current when plugged into shore power is the boats connection to the green wire. Every boat on the dock that is plugged into the shore power is now essentially part of your boats bonding system. Your anodes that are protecting your under water hardware are also protecting the boat next to you if it is plugged into the shore power pedestal. The Galvanic Isolator helps to disconnect your boat from the boats on the dock while plugged into shore power. The isolator will allow the grounding system to work but only one way protecting your boat and you.

You stated that no matter where you go different marinas and piers you have the same amount of "leakage" . Your technician suspected that the ACR is the issue. Open or closed will not cause the issue if the ACR has failed. The only cause could be an internal failure where DC current is leaking through the 14 gauge ground wire used to complete the internal circuit of the ACR. A call to Blue Sea would be in order to hear their thoughts. I believe the ACR causing this "Electrolysis issue is a stretch but if your are measuring an increase in milli amps in the bonding system with the ACR connected and then a drop when disconnected this would indicate a problem.

What type of anode are you using? I recommend that with the outboard the use of aluminum anodes. This will not fix your issue but will help possibly extend the erosion time. If you are seeing damage to the gear case and under water components I would rectify the issue before replacing items that need repair. You C24 is not the only C24 that has had this issue. I have talked to others with the exact issue and have had to replace the Lower unit because of damage.

Below is a link to one of many threads about this TugNuts
viewtopic.php?f=2&t=14650&p=100980&hilit=lower+unit+corrosion#p96959