Mercury - Power Trim Relay Electrical & Trim System Marine-Grade 8M0207773. Overview. If you've spent any time running shallow channels at sunrise or easing your way onto a trailer in a stiff crosswind, you know just how much you rely on your trim system. When it works, you barely think about it-you just feel the boat respond the way it should. That trust is something you don't gamble with. The Mercury Power Trim Relay 8M0207773 gives you that same steady confidence every time you tap the switch