Mercury - TVM Harness (No Rig) Rigging Accessory 8M0191737. OverviewThis TVM harness is the missing link for setting up electric steering on 250-300 HP V8 Verado engines, whether you're running Joystick Piloting or a non-joystick electric-steering setup. It gives each actuator its own clean connection so the system can run the way it's designed to. The harness keeps the wiring simple and avoids the headaches that come from trying to adapt pieces that weren't meant for the job. Once installed, st