Mercury - Quicksilver Exhaust End Cap Riser Gasket Crusader & Mallory Replacement Marine-Grade Sealing Component 8M0162539. Overview. If you've spent enough time around inboard engines, you know the smallest parts often carry the biggest responsibilities. A riser gasket might not look like much when you pull it out of the package, but the moment you bolt everything back together and fire up the engine, you're reminded of how important a clean, dependable seal really is. The Mercury Marine part n