Sierra 18-99452 2-Cylinder Ignition Trigger - Mercury MarineSierra Marine SIE-18-99452 Ignition Trigger is a precision timing sensor designed for select Mercury 2-cylinder outboard engines. It monitors flywheel rotation and sends accurate timing signals to the ignition system for proper spark control. This unit is built for 19951999 Mercury 30HP and 40HP engines with TPM modules and replaces OEM ignition trigger components for reliable engine performance.Key Features 2-cylinder marine ignition trigger sensor; Fits 19951999 Mercury 30HP and 40HP engines; Designed for engines with TPM modules; Replaces Mercury OEM 99021A11 and 99021A14; Equivalent to CDI Electronics 134-9021-2; Interchange: CDI Electronics: 134-9021-2; Mercury Marine OEM: 99021A11, 99021A14;