Mercury - Quicksilver Low-Oil Switch Assembly Engine Protection Resin-Encapsulated Construction 856156T04. Overview. There's a certain calm that settles in when you know your engine is watching out for you as much as you're watching the horizon. That's exactly what you feel with the Mercury Marine part number 856156T04 Low-Oil Switch Assembly on board. It's the kind of quiet confidence that lets you push out a little farther, stay out a little longer, and trust that your engine will speak up whe