Mercury - Oil Pump Assembly OptiMax & Diesel Series Marine-Grade Construction 8M0185614. Overview. Every boater knows there's a certain peace that comes when your engine runs the way it's supposed to - smooth, steady, and trustworthy. That's the kind of confidence this Mercury Marine part gives you. An oil pump may not be something you show off, but you sure feel its importance when you're running far from the dock. With this assembly in place, you know your outboard is getting the oil flow it n