Mercury - Driveshaft Housing Oil Seal Sterndrive Seal Marine-Grade Construction 965031. Overview. There's a certain trust you build with your sterndrive over the years-the kind that comes from smooth shifts, steady acceleration, and a hull that responds exactly when you need it to. But every seasoned boater knows that keeping a MerCruiser running strong isn't about luck. It's about maintaining the small things before they become big problems. The Mercury 965031 Driveshaft Housing Oil Seal is one