Mercury Gearcase Drain Plug Gasket Part 354 (5-Pack)

Mercury Gearcase Drain Plug Gasket Part 354

This genuine Mercury OEM drain plug gasket is a small but essential sealing washer used on the drain and fill screws of older Mercury outboard lower units and gearcases. It creates a leak-free seal that keeps gear lube in and water out. Sold in a convenient 5-pack the right quantity for multiple services or keeping spares on hand.

Compatible Applications

• Older Mercury and Mariner outboard lower units using Part 354 drain plug gaskets
• Confirm fitment against your engine model and serial number newer Mercury engines use the updated 8M0187157 blue seal

Part Details

• OEM Part Number: 354
• SKU: 530451
• Brand: Mercury / Quicksilver
• Type: Gearcase drain and fill plug gasket (sealing washer)
• System: Lower unit / gearcase
• Pack Quantity: 5 gaskets
• Condition: New OEM

Service Interval

Replace this gasket every time gear lube is changed. The gasket compresses on first use and should never be reused reusing a spent gasket is a leading cause of gear lube leaks after service.

Technical FAQ

• How many gaskets do I need per service? Most lower units have two screws a drain and a fill/vent so use two gaskets per service. The 5-pack covers two full services with one spare.
• Is Part 354 the same as 8M0187157? No Part 354 is the legacy gasket used on older Mercury outboards. The 8M0187157 blue seal is the current OEM replacement for newer engines. Check your engines service manual to confirm which part applies.
• Can I reuse the old gasket? No. These are one-time-use sealing washers. Reusing a compressed gasket risks an incomplete seal and gear lube leaks.
• What happens if I skip replacing the gasket? A missing or reused gasket can allow gear lube to seep out and water to enter the lower unit, leading to bearing and gear damage.

Related Parts

• MerCruiser Gearcase Drain Screw Seal 8M0187157 (Blue) current OEM replacement for newer engines
• Mercury MerCruiser Gear Lube Pump Kit 8M0072135
• Mercury Lower Unit Seal Kit 26-33144A2

Parts Desk Insights

Part 354 is the legacy drain plug gasket for older Mercury outboards if youre servicing a newer engine and this part doesnt look right, check whether your engine uses the 8M0187157 blue seal instead. The most common mistake with drain plug gaskets is reusing the old one: these are one-time-use compressible washers, and a reused gasket is one of the most frequent causes of post-service gear lube leaks. The 5-pack is the right buy for anyone doing regular seasonal maintenance on one or more outboards at this price point, theres no reason to risk a leak by reusing a spent gasket. Always confirm your engine model and serial number if youre unsure which drain gasket applies.