Mercury - Dash-Mounted Catalyst Malfunction Light Engine Alert Indicator 8M0046481. Overview. Catalyst-equipped MerCruiser engines rely on a clear visual alert when the emissions system needs attention. The Mercury 8M0046481 Dash-Mounted Catalyst Malfunction Light gives you that reminder. When the catalyst system detects a fault, this light turns on-much like the check-engine light in a car or truck-letting you know it's time to get the engine inspected. It's simple, easy to see, and built for d