Mercury - Under-Helm GPS Mount Kit SmartCraft / NMEA 2000 98-8M6009519. Overview. Some helm layouts don't have the space for a top-side antenna mount, and that's where this compact under-helm solution comes in. The Mercury 98-8M6009519 Under-Helm GPS Mount Kit creates a clean, protected mounting point beneath the helm or console for SmartCraft or NMEA 2000 GPS antennas. It keeps the antenna secure, out of sight, and positioned for dependable signal reception. It's the same under-helm mount inclu