Yellow is the new black (for marine DC wiring)
LaRea
Member, Moderator Posts: 7,930 mod
Public service announcement. The boating safety group ABYC recently started phasing in a change to its recommended wire color scheme for DC power wiring.
Old: red = 12V positive, BLACK = 12V negative
New: red = 12V positive, YELLOW = 12V negative
Historically, black wires were used for two purposes: DC negative wires, and also AC hot wires (120V supply from shore power or generator). Confusion between these types of power could be deadly, so ABYC now deems it safer to use yellow for DC negative.
There's no need to rush out and rewire your entire boat. But in repairs or new wiring projects, consider using yellow for DC negative wiring. And if you add new components, don't be surprised if they have red/yellow power wiring instead of red/black.
My favorite wire for DC power is ANCOR "safety duplex wire" which is red and yellow conductors in a white jacket. It's a really nice product: well-protected, flexible and easy to work with.
There's no need to rush out and rewire your entire boat. But in repairs or new wiring projects, consider using yellow for DC negative wiring. And if you add new components, don't be surprised if they have red/yellow power wiring instead of red/black.
My favorite wire for DC power is ANCOR "safety duplex wire" which is red and yellow conductors in a white jacket. It's a really nice product: well-protected, flexible and easy to work with.

Comments
I have not adopted red/yellow in my boat, and I didn't change any of the legacy wiring. But I figured it would spark a conversation (pun intended)!
Go Steelers!!!
On one hand, mixing the two conventions might confuse a future owner. On the other hand, your boat already has mixed wiring, so adding more yellow wouldn't add much confusion. On the OTHER other hand, an express cruiser has relatively simple wiring, so either way the risk of confusing AC and DC wiring is small.
I guess I'd use yellow, just on general principles. But if you're buying wire and can only get red/black, use it and don't sweat it.