Yeah, those cracks are surely an issue.  But, I’m not sure the pump would actually pull air through there because those cavities seem to be isolated from exhaust as well.  Nonetheless, Those cracks may be keeping the SS impeller plate from fitting flat on the gearcase and sealing properly.  That casting is pretty thin and relatively delicate, so I really don’t think it could be welded without causing further damage.  I would look for a decent gearcase or housing next winter.   I wouldn’t waste your time trying to used JB weld or some other epoxy/glue.

My experience with freeze damage is somewhat limited, down here in Florida where the current water temperature in the Gulf Of Mexico is edging up toward 100 F.  But I have seen such damage on motors that were dragged down here from Upnorth, Canada.

1 user thanked author for this post.

bob-d