I feel foolish because I've changed the oil plenty of times before. I have a built-in pump for draining the oil. It was installed before I bought the boat so I can't say how it's plumbed. I ran the pump until it was just spurting but only got maybe a gallon of used oil out. The 4.108 holds 2+ gallons, correct? Is it possible there is another gallon or so still in the engine somewhere? Do I need to pull the plug on the oil pan too?