Mercury optimax 3 cyl DFI serpentine belt 57-892318 57-8M0026410 Mercury optimax 3 cyl DFI serpentine belt. This replaces Mercury 57-8M0026410 and 57-892318. This direct replacement belt is made to the same manufacturing standards as OEM and are used by most engine manufacturers. 4 rib serpentine belt. 1 year free replacement warranty.