Mercury - Timing Belt EFI FourStroke Marine-Grade Composite 8M0186928. Overview. Anyone who spends real time on the water knows there's a certain comfort that comes from an engine that fires up cleanly, settles into a smooth hum, and just does its job without fuss. A reliable timing belt is a quiet hero in all of that-a part you rarely see but always depend on. The Quicksilver 8M0186928 Timing Belt gives Mercury 25 and 30 horsepower EFI FourStroke owners that same sense of confidence, whether yo