Mercury Nut - 11-18304. The Mercury Nut - 11-18304 is a genuine OEM replacement component designed for precise fit and secure fastening within Mercury marine engine assemblies. Built to Mercury's exact engineering standards, this critical nut ensures long-lasting performance and proper structural integrity in high-vibration marine environments.. Key Features. OEM Precision Fit - Manufactured to Mercury's exact specifications. Corrosion-Resistant Finish - Built for durability in saltwater and freshwater conditions. Thread Integrity Guaranteed - Engineered to maintain tight tolerances under load. Essential for Engine Assembly - Used in critical mounting and retention applications. High-Grade Materials - Ensures strength and long service life. Compatibility. The Mercury Nut - 11-18304 is compatible with various Mercury and MerCruiser engine models. For best results, confirm your engine's part diagram or consult with PartsVu's support team to ensure this nut is the correct replacement for