Mercury - Power Trim Switch Outboard Control System Marine-Grade Rocker Style 8M0042301. Overview. If you spend enough time on the water, you start to appreciate the small things that make a boat truly enjoyable to run. A good trim switch is one of those unsung heroes. With one quick tap, you can bring the bow down into a steady ride or lift it just enough to skim across calm water. When that switch starts sticking or hesitating, you feel it in every wave.. The Mercury Marine part number 8M00423