Mercury - Troll Control with Y Harness Dash Mounted Analog RPM Control 8M0083439. The Mercury Troll Control with Y Harness Dash Mounted is designed for boaters who want consistent, hands-off RPM control during slow-speed operation. It is commonly used on boats equipped with analog gauge systems where fine throttle adjustments are important, particularly while trolling. The dash-mounted control integrates cleanly at the helm and connects through an included Y harness for a straightforward, organi