Originally Posted by Jgbrown
Could running a generator and sharing the power with another boat cause electrolysis?
At work I have a customer who has self installed a 30a shower power outlet connected to his generator. He uses this to share power with other powerboats he's rafted up with while on vacation.
No protection or isolation of any kind.
Props, struts and drive shaft were badly corroded on the port side, starboard showed minimal corrosion, perfectly acceptable.
new shaft going in, as a result of the large pits and defects. It ate away the bolts on the line cutters on the shaft so much that the heads were essentially gone requiring it to be cut apart.
I'm looking for potential sources, my boss has asked me to research the issue and write up a bit of a paper for the customer on both the risk, and the potential harm to the boat.
I'm hoping to do a really good job, since my boss is going to pay for my ABYC certification in the spring, and is looking for me to show some effort and initiative in figuring this one out.
I would suspect a DC corrosion issue. DC corrosion is MUCH FASTER and is, in most cases, caused by your own vessel. People often attribute heavy corrosion to AC leaks but this is highly improbable.
You should to start with the "bonding wires" or the copper wires either bare or green that are connected to all the underwater metals like the seacocks, struts, engine, rudder posts etc. etc... Insert a DVM on the "amp" setting, into a green wire, closest to the battery bank, and then begin firing up components and watching the DVM. It is significantly to have a high sensitivity AC/DC clamp meter like the Extech or Amprobe shown below to trace these down, as it makes it far easier..
With that amount of corrosion it is likely you have an on-board device using the bonding or earthing circuit to pass current, which should not be. This vessel should also have a galvanic isolator or isolation transformer. If there is a galvanic isolator it should be tested to make sure it is functioning.
You will also want to plug into the shore power and put a very sensitive AC clamp meter (must read to the hundredths 00.01A and have decent accuracy at low current) around the entire
shore power circuit. Now turn on your AC devices one at a time, water heater, microwave, fridge, battery charger etc. etc. and see if you get a reading.
If you get any current reading on the shore power cord then you have a leak.. With the meter clamped around the cord the reading should be 0.0.. If you start seeeing 0.02 - 0.4A you have a leak and current is taking the green wire. This is often just bad connections or corrosion on the other side of the circuit causing current to flow back on the green wire but it culd be a faulty battery charger, water heater or other on-board device or a chafed wire shorting to ground somewhere.
If you don't have a clamp meter than you'll need to insert a standard DVM into the green/ground wire. There should be no current on this wire..
Here are two suitable clamps for measuring corrosion level leaks on boats:
380942 - 30A True RMS AC/DC Mini Clamp Meter
Amprobe (A Fluke Company)
LH41A AC/DC Low Current On Clamp Ammeter | Amprobe
Complete those tests first, then we'll get you to buy more tools....