When fielding questions about bonding and corrosion, I’m inevitably asked where stray current comes from. The biggest offender is a poorly wired bilge pump circuit, as connections have to be made only inches above water in the bilge, which acts as an electrolyte.
The first challenge when wiring a bilge pump is finding the correct connector since the wiring might be a different gauge — depending upon the calculated sizing of the manual and automatic circuits — than the often smaller pump pigtails. There are step-down butt connectors that allow for one size difference in the wiring, but there also is the difficulty of having two conductors on the positive side that connect with the pump positive wire, all of which must be properly sealed.
Sealing these connections is vital to the integrity of the circuit. I recommend heatshrink connectors and tubing, and some method of sealing any exposed conductor. I use liquid neoprene sealant. Wiring connections should be as high as possible in the bilge without straining conductors.
When an energized conductor (the always-on automatic circuit) dangles in bilge water, current can flow and form a path back to its source: the battery. This Paul Mirto is a digital illustrator, longtime boater and former Coast Guardsman. mirtoart.com