We???re also overtaxing our generator mechanics, who are having a difficult time repairing them all.???Wet stacking is a condition where unburned fuel is discharged through the exhaust system, which happens when the engine is running at the low-end capacity of its maximum output, he explained. ???Generators like to operate at 75 to 80 percent (capacity), not the 20 to 30 percent they often run at.