Sierra MP51090 Mercury Ignition Switch 3 Position Sierra MP51090 Mercury Ignition Switch replaces Mercury Marine OEM Part 87-17009A5. Features Exact OEM replacement installation Heavy duty potted construction Minimal bleed per circuit Molded umbrella type key Push to choke Maximum corrosion protection - eliminates oxidation Inner seal between cylinder lock and contact plate Non-conductive housing eliminates potential shorts Specifications Back Up Nut Not Required Face Nut Hex Black Plastic Hole