Mercury - Propeller Washer Prop & Drivetrain Hardware Series Hardened Stainless Steel 887972. Overview. Every boater has felt that subtle moment of reassurance when the prop bites cleanly and the boat moves forward without the slightest slip. It's the kind of confidence you don't think about until something feels off - a vibration, a hesitation, or a strange noise that wasn't there yesterday. The Mercury Marine part number 887972 Washer is one of those small but essential pieces that keeps every