Mercury Manual-Owners - 90-89464. The Mercury Manual-Owners - 90-89464 is your go-to reference for properly operating and maintaining your Mercury engine. Designed by the original manufacturer, this official guide gives you trusted, model-specific instructions that help you maximize engine performance, prolong service life, and enhance safety every time you're on the water.. Key Features. Official OEM Manual - Developed by Mercury for reliable and precise information. Covers Daily Use & Routine