Mercury - Remote Control Ignition Choke Extension Harness Wiring Extension 84-17829A10. 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 on larger boats, dual-station setups, or repower installations where existing ignition and choke leads do not comfortably reach. Using a proper extension harness helps maintain clean rigging and avoids stretching wiring or creating spl