Trying to isolate electrolysis issue

Hey SeaRay members,

I am trying to isolate an electrolysis issue that reared its ugly head last season. Previous seasons all was ok. We recently installed 30AMP shorepower so I am thinking that may be the culprit. Can a Marinco locking receptacle that does not fully lock cause the issue? Can I test somehow?

If it is the receptacle and we fix how can we test to ensure the problem has been corrected?

Thanks so much!! Vin

What is the issue?
If it's the GFCI popping, that could be from mandates having recently dropped the limit from 100ma down to 30ma. That was set sometime in 2017, IIRC.
Do you have an isolation transformer on your incoming shore power line? If not, consider adding one.
Make sure that the shore power's ground is not somehow connected to any internal-to-the-boat's ground system.

Thanks for your reply.

Issue is that the outdrives had some really bad corrosion. Mechanic said is was from electrolysis and need to find out what was causing and fix.

There’s no GFCI and no iso transmitter. (Will look into that)

Can the Marino receptacle which did not fully twist lock be the cause? Power worked fine but wondering if the ground might not have been fully grounded due to the plug not fully locked in the receptacle.

Oh boy. I had similar problem. Even hired electrical contractor to come to my slip.

Short version. Almost impossible to find and then fix. I lost a Bravo drive. Bottom split in half.

I had that outdrive sandblasted primed and painted. Nope.

Once the current is in the metal you can’t get it out is what I was told and turned out to be true in my case.

Main reason I’ll never slip in salt.

Do you have a galvanic isolator installed? An isolation transformer would be better, but as a minimum, any boat with shore power should have a galvanic isolator. I would also have a marine electrician look at the shore power installation and ensure that the green wire is properly connected. By any chance are you using a portable (non-marine) battery charger on the boat?

Couple of suggestions: 1) makes sure your bonding straps are intact, 2) make sure you are using the right alloy in your anodes for the salt water environment, 3) make sure your outdrives are not in contact with your bottom paint, 4) make sure all drive components are painted heavy with a proper paint (ie trilux 3 on bravos), 5) if you have a mercathode system verify it is intact and working.
lastly check your slip with a reference electrode and voltmeter to check to see if your slip is "hot".

-Kevin

X 5...

Had the same problem. Destroyed a 4 trim cylinders! Ate through my skegs. I am at a new dock with GFCI protection too.
Installed a galvanic isolator (extra heavy duty) last season and heavy duty anodes on my trim tabs. Helped a lot. Bottom line, check you anodes regularly. They should go first before the drives. Get a mid season haul and replace them if needed! It's a lot cheaper for a quick haul out than a drive!!! Note: If you have stainless props on an Aluminum outdrive, you already have a battery in the water causing corrosion.

Galvanic corrosion is the condition. It is caused by the erosion of the lesser noble metals to, in this case, water due to electrical current. It will occur regardless of conditions but abided by exposing the lesser of noble metals as anodes like Zinc, Magnesium, or Aluminum. In your case Aluminum. There is always electrical current and typically in a healthy protected system the current is miniscule and the boat's zinc anodes manages the corrosion. If, however, there are other electrical leaks to the boat's grounding/bonding system then the corrosion can greatly increase. The key is to have a good AC power system and fully intact and integrated grounding and bonding system. A couple of FYI's -
Bonding - All of the boat's metallic elements must be bonded to a common electrical network (the Green wires) and that network must be bonded to an anode mounted to the boat's hull. That anode which is zinc in salt water and magnesium or aluminum in fresh water is the sacrificial material and consequently requires replacement.
AC Shore Power - It is important to isolate the shore power ground from the boat's grounding and bonding system from a natural current aspect. This is the purpose of the galvanic isolator or the intrinsic ground isolation of an isolation transformer. FYI a galvanic isolator prevents natural current from flowing between the boat and shorepower but allows fault current to the shore power ground network. If a boat's neutral wiring of the AC power system is by chance faulted to ground then there will be greatly accelerated corrosion due to the electrical current passing through the boat and to the water around the boat. If you have a generator then when on generator power the boat's AC neutral is bonded to the ground but when switched to shore power that neutral is disconnected from the boat's ground; check that.
GFCI - There is typically GFCI protection on you boat and most marinas are also now protected. This has nothing to do with galvanic corrosion; in fact, the GFCI protection can enhance corrosion protection in that the GFCI removes current if the electrical current is not balanced between the Hot and Neutral conductors. So if in an AC electrical system there is a fault where current is leaking to ground the GFCI senses an imbalance between the Hot and Neutral and will trip the system off line.
Boats and Structures around your boat - Electrical faults in systems and boats in the vicinity of your boat can cause negative results and corrosion in your boat. Your marina should have a test instrument to determine electrical leakage in the water around the marina. Get with them to "test the water"....
Mercathode - This is propriety to Mercury but essentially the system imposes cathodic current to counter galvanic corrosion.

Pugli-Sea said:

Thanks for your reply.

Issue is that the outdrives had some really bad corrosion. Mechanic said is was from electrolysis and need to find out what was causing and fix.

There’s no GFCI and no iso transmitter. (Will look into that)

Can the Marino receptacle which did not fully twist lock be the cause? Power worked fine but wondering if the ground might not have been fully grounded due to the plug not fully locked in the receptacle.

Click to expand...

I would not suspect the twist lock, Twisting to lock does not affect the contact to the ground. Contact is made once the plug is mated to the receptacle. The lock is just to keep it in place. if it is not locking though it may be because the prongs are loose and are shoved into the insulator body. Both of mine on the 44 were loose and I constantly had to pull them out to their full length prior with a pair of plyers prior to connection to get the plug to twist and lock. I believe you implied that the shore power system has been added to the boat and not a factory install. I would seek the assistance of a trusted, knowledgeable marine electrician to trouble shoot your issue and check that the shore power system is installed correctly.
Good luck, I dealt with this stuff on my Rinker in a marina with several derelict boats and often wondered if they were major contributors to my issue. I never had an issue with the 44 and it was in the same slip for three years so I attributed the issues with the boat's out drive and ground installation.
Carpe Diem

Pugli-Sea said:

Hey SeaRay members,

I am trying to isolate an electrolysis issue that reared its ugly head last season. Previous seasons all was ok. We recently installed 30AMP shorepower so I am thinking that may be the culprit. Can a Marinco locking receptacle that does not fully lock cause the issue? Can I test somehow?

If it is the receptacle and we fix how can we test to ensure the problem has been corrected?

Thanks so much!! Vin

Click to expand...

So prior to this year you did not have ANY AC electrical on board correct?
And prior to this year you did NOT have any corrosion/electrolysis issues correct?
Who designed and installed the AC power?
Do you have an AC generator?

As some have pointed out, AC has to be connected to a boat in a very specific manner or you will have ground faults, electrolysis and/or safety issues.

125VAC 30A power has Hot (black), Neutral (white) and Ground (green) wires.
On land ground and neutral will go to a common connection at the main panel only. On a boat the two must never be connected together in the boat AC panel. They MUST be connected together at an onboard generator, but that should be isolated from the boat AC panel by a shore/generator set of breakers (or a switch) when operating on shore power. The green ground wire to shore socket should have a Galvanic Isolator installed inline.
The panel should have a "reverse polarity light" that protects from having the white and green reversed in the shore cord or sockets. Without a properly wired indicator light it is very difficult to detect reverse polarity wiring as everything will appear to work normally.

This professional blog provides all the diagrams and has a great deal of details if needed.
https://shop.pkys.com/How-to-install-a-simple-shore-power-system-on-a-small-boat_b_86.html