Mercury - Distributor Assembly Ignition System High-Strength Polymer & Marine Alloys 879150A87. Overview. Anyone who's spent years running MerCruiser engines knows how much the ignition system shapes the way the boat feels on the water. When the spark is right, the engine wakes up with a smooth, eager note that pulls cleanly through every throttle position. This Mercury Marine distributor assembly brings that feeling back. It's built for boaters who want their engine to run steady, clean, and pr