Aluminum Hulled Sailboat - Stray Current

[SoggyHalyard]

Hi all,

I recently purchased an aluminum sailboat and am in love. The boat is a beast. We had an extensive survey done and the hull is in great shape. No signs of corrosion. Problem is, I just checked for stray currents by installing a leak detector from dolphin and the gauge is maxed out (above 8mA).

The boat is ~45' with solar, wind, 2 DC panels, and no generator. So the electrical system moderately complex.

I'm hoping to get some advice on where to start. I'm a bit overwhelmed and am concerned that we have many circuits with leaking current so unplugging them one by one and trying to identify a change using the simple gauge may not be effective.

Anyone out there been in this situation?

[osprey877]

I'm not an electrician, but instead of unplugging loads one by one, I would first disconnect the shore power, the solar and the batteries and check that I got a zero reading. If not, then maybe stray current originates off the boat? See if you get same readings in a remote anchorage away from marina? If source on boat, then maybe you will have to try each load separately.

[double u]

check on leak from engine first, they are very difficult to isolate 100% from the hull. Have a vented loop before the saltwaterpump, so there is no connection via the saltwater in the cooling circuit.
Have a heavy switch in the ground going to the engine & turn it off, when the engine is not in use.

[noelex 77]

Congratulations on the new boat.

If you have double pole isolation of the circuits, this is an easy problem to track down.

Turn all circuits off. The stray current should disappear. Then turn on the circuits one by one until the fault occurs. You then need to trace the defective circuit and eliminate where it is in contact with the hull.

[Bowdrie]

Originally Posted by SoggyHalyard

Hi all,
I just checked for stray currents by installing a leak detector from dolphin and the gauge is maxed out (above 8mA).

Others have already commented on several things/areas to start investigating.
On metal boats, (particularly aluminum,) the need for prevention of stray electron flow should be approached with almost a religious fervor.
Are any devices such as inverters/battery chargers/refrigeration units/water heaters, etc., directly fastened to any metallic framing or brackets that are in contact with the boats structure?
It's all detective work.
Engines can be totally isolated, and the first step, (of several,) is not using the engine as a "Grand Central Station" bus bar with a plethora of wires and using something like a "Drivesaver" to break the electrical path to the prop shaft.

[skipperpete]

Bilge pumps, vhf antennas, engine control cables and engine alarm circuits are all potential culprits. I’ve had to convert a number of engines to “above ground” wiring when repowering alloy vessels, mostly Ovni’s but several larger boats too. You need to get this right and I’m surprised your new yacht didn’t already have the leakage detector installed from new.