Winterizing 5.0 Mercruiser Question

[25thmustang]

So this past weekend was my first go at winterizing a sterndrive (raw water cooled) boat. I have experience with my inboards, but have yet to tackle an I/O. So as the methods I researched and used on my motor, I went first with fogging the motor. Once fogged, I found the six drain plugs, two on the block, two on the manifolds and two on the risers. So off came the drain plugs and hoses at the front of the motor. We used a wire to break up any debris plugging the holes, and got a great flow at each one. Once each plug (starting low and working up) was flowing punk antifreeze, I reinstalled it and went to the next. The starboard side went easy. The port side went fine other than the lowest block drain. I was able to get the wire stuck into that hole a good 6". I was getting a stream of water but not water pouring out, as with the other 5. It was pink antifreeze, but did not make sense why this area of the block wasn't getting a good flow of water.

I am going to assume either some corrosion further up, somwhere in the block causing a blockage, or potentially a piece of the water pump impeller? Is there anyone here who has had a similar experience and what was the solution?

Also other than tilting the outdrive down, flushing antifreeze back through the hoses and covering it with a bag, are there any other suggestions on winterizing the outdrive?