Mercury - Diesel Vessel Sensor Harness Inboard Sensor Wiring Harness 84-899887T08. The Mercury Diesel Vessel Sensor Harness is designed for diesel inboard applications where optional vessel sensors must communicate reliably with the engine system. It provides a centralized, protected connection point that keeps sensor wiring organized while maintaining clean, stable signal transmission throughout the electrical network.. This harness supports both DTS and non-DTS diesel inboard setups (excluding