Mercury - Quicksilver Distributor Assembly For V8 MerCruiser Engines with Thunderbolt IV & V Systems 805185A36. Overview. A strong spark means a strong engine, and the Mercury Marine 805185A36 Quicksilver Distributor Assembly keeps your ignition system delivering just that. Designed for marinized V8 MerCruiser engines built by General Motors, this complete distributor kit supports Thunderbolt IV and V ignition systems - restoring crisp starts, smooth idle, and steady power. Built from durable, m