Mercury - Dual Engine Key Switch Harness Kit Non DTS Fourteen Pin Ignition Wiring Kit 896537K25. Overview. This dual engine key switch harness kit is built for mechanical Mercury outboards that need synchronized ignition control from a single helm. It's commonly used on twin engine boats with wide consoles where clean routing and matching components matter. The paired twenty five foot harnesses provide plenty of reach without stretching or forcing connections. It's a straightforward solution tha