Mercury - GPS Extension Cable 9.8-Foot CAN P Line 84-879171T23. Overview. Longer boats and wider helm layouts sometimes need more reach than the factory GPS cable provides. The Mercury 84-879171T23 Extension Cable adds 9.8 feet to the GPS line used with the 8M0024918 kit, giving you enough length to route the antenna cleanly across larger consoles or more spread-out rigging paths. Built for CAN P GPS systems without an Auto Pilot module, it extends the signal without adding noise or setup steps.