Block Chimney Repair

[we're golden]

I have a cinder block chimney that I believe was built in the mid 70's. I can see cracks in not only the seams, but also running through the blocks themselves. In the spring after the heavy rains, and entering the house after it has been closed up for the week, there is a strong ash smell. Can anyone recommend a product that I can apply that would seal the exterior of the chimney? Any help would be appreciated.