Electrolysis Woes

[frank balcer]

Just purchased a new to me 37 foot Kirie Elite. Boat was hauled in April and two shaft anodes installed by former owner. As of this week one is completely gone and second one fell off in my sons hand as he was underwater scrapping my propeller. Boat has one 12 volt starting battery and four 6 volt beep cycle house battieres (hooked in pairs). All fives batterys are connected to a bulkhead mount charger that runs continuously when im hooked to shore power in my slip mainly to keep my refrigerator cooling. Any ideas where to start looking for the cause of this quick electrolysis? Thanks...... frank

 

[KD3PC]

if your stuff checks out, (see below) it could be a ground or neutral issue....likely on the marina side....or poor systems on a boat near you...any big, old, nasty, power boats, or neglected sail ones ?

want to be careful with "their" stuff....if you open their covers, and something falls apart, they will want you, or a licensed electrician of their choice, you paying of course, to fix it.

I would start with a simple "socket checker" and check the 15/20 amp outlets on your boat, whilst plugged in, then if you have a L30 to regular plug adapter, do that and if that all checks OK, then you are to a multimeter and such trouble shooting as continuity between shafts and engines, battery banks, etc

 

[kloudie1]

Wow.. that is a problem.. Get a zinc "fish" and hook to engine ground to buy some more time while you put on two more prop shaft zincs ((former owner didn't use magnesium, did he? that would account for the rapid disappearance) Next, after doing the checks noted by kd, is to get an electrolysis survey done, using a reference cell, to identify the problem.. A good marine electrical guy will be able to do this for a lot less than the cost of a new propeller and strut. Until that is done, it would be guessing.. You are probably going to have to install a galvanic isolator, but that too is a guess.

 

[Don S/V ILLusion]

A galvanic isolator will prevent the A/C side from causing this. Typically though, the problem is on the DC side. I'd start by checking all wiring to ensure you have only one path to ground - multiple grounds create electrolysis. also check the other obvious stuff like an uninsulated wire in the bilge, engine, etc...
These problems are not easily solved on the internet so if you can't find the cause, have someone who knows what they are doing take a look.

 

[Maine Sail]

Just purchased a new to me 37 foot Kirie Elite. Boat was hauled in April and two shaft anodes installed by former owner. As of this week one is completely gone and second one fell off in my sons hand as he was underwater scrapping my propeller. Boat has one 12 volt starting battery and four 6 volt beep cycle house battieres (hooked in pairs). All fives batterys are connected to a bulkhead mount charger that runs continuously when im hooked to shore power in my slip mainly to keep my refrigerator cooling. Any ideas where to start looking for the cause of this quick electrolysis? Thanks...... frank

Call the ABYC and ask for a technician who is an ABYC Certified Corrosion Specialist or do a search in the directory below..

ABYC Certified Technician Directory

There are far to many variables for a DIY to even begin to try and tackle this or to even try and sort it out on-line. It only gets more complicated with the tools needed to trace this down, which most boat owners just don't own....

Most corrosion issues that happen as fast as you depict are caused by the boat it is occurring on not necessarily by other boats.. This is likely an on-board DC issue. Cheap battery chargers & bilge pumps can be two of the big culprits..

 

[SEMIJim]

Most corrosion issues that happen as fast as you depict are caused by the boat it is occurring on not necessarily by other boats.. This is likely an on-board DC issue. Cheap battery chargers & bilge pumps can be two of the big culprits..

That nearly identical to the answer I would've given, but I decided against answering as, tho I understand the principles involved, I've no actual expertise in this area.

Except I was also going to point out, to those that implied it was a "shore power issue," that, as I understand it, that is probably only true insofar as the shore power connection is providing a common connection, via the earth ground wire, between his boat and others. Thus, if the problem is another boat leaking DC: Removing that common connection, by disconnecting from shore power, should cause the problem to abate. Conversely: If his own boat is the source of the leak: Disconnecting from shore power won't help him, but it may stop him from causing his neighbours' boats' submerged metal bits from being eaten at an accelerated rate.

Jim