Mercury - Remote Control Ignition Choke Extension Harness Wiring Extension 84-17829A2. The Mercury Remote Control Ignition Choke Extension Harness is designed to provide additional wiring length between the helm control station and the engine. It is commonly used during repowers, dual-station installations, or console relocations when the original ignition and choke leads do not comfortably reach. Using a proper extension harness helps maintain clean, organized rigging without resorting to splic