I am winterizing my 1988 OMC 4.3L. I already drained the engine block, manifolds, and power steering cooler. The book says all you need to do to drain water from the outdrive is remove the water drain plug on the port side of the drive. When I removed it no water came out. I was curious, so I removed the water pump and sure enough there was still water in the left hole behind the pump. None in the right. When I poured water into the right hole, it came out the right side intake on the lower. Nothing is draining from the left side. What is going on here? Is something blocked or plugged?