Thanks for the video.
I don't usually close the valve on this boat, it's not easy to get too as the old boat. We've had some crazy cold (-18F) weather lately and I was being cautious.
The impeller is easy to change, did it 6 months ago. I still need to find/remove one missing vane, probably more now. I have two spare impellers, but not for long.
There are 2 things that you said here that grabbed my attention.
First, if you have a missing vane from a previous failure, you need to find the piece(s). The broken bits will cause a clog that can be harder to fix. I wouldn't run the engine until you know there are no obstructions. Perhaps it even has something to do with feeding water to the dripless system. On that note, I am unfamiliar with that system, but I suspect that you might simply have had trapped air in the bellows and if you "burp" it you should be all right. I'm more familiar with PSS, though, where the water comes in directly from the shaft tube.
Second, are you saying that your boat was in the water with -18F weather? Do you not take the boat out of the water in the winter? If you leave the boat in the water in freezing temps, I think that I would be inclined
NOT to close the valve during freezing weather. Wouldn't the water under the boat stay unfrozen. If you close the valve, aren't you trapping water inside the valve and in the hose (up to the water line) that is
MORE inclined to freeze as it is exposed to the freezing temps inside the boat?
I would assume that it is safer to leave the valve open where it is exposed to unfrozen water and there is at least a chance that freezing water has a chance to escape out the bottom as it expands and creates pressure. I'd be afraid that a burst valve would sink the boat and it isn't going to be water underneath the boat that freezes.