Thermostat Gasket SIERRA 118-0398-9

Compatible Engines

The SIERRA 118-0398-9 thermostat gasket is a critical component ensuring the sealing of the cooling system in popular marine propulsion units. This part is primarily dedicated to MERCRUISER, OMC, and VOLVO PENTA engines with displacements of 10/120 and 140/150/160 horsepower (in 6-cylinder configuration). This version is also used in boats equipped with MCM 3.0L / LX engines featuring a closed cooling loop. Please note that compatibility should always be verified by the manufacturer's catalog number 118-0398-9 or the original OE number. If in doubt, contact our support team.

Installation and Operation

Proper replacement of the gasket is essential for maintaining optimal engine operating temperature. We recommend thoroughly cleaning mounting surfaces from deposits before installing the new part. Using original SIERRA gaskets minimizes the risk of leaks and failures.

• Original Quality – SIERRA product guarantees durability and compliance with standards.
• System Seal – prevents loss of coolant and overheating.
• Easy Installation – simple replacement in standard boat service centers.
• Wide Compatibility – fits many MerCruiser and Volvo Penta models.