Old Cast Iron Wood Water Boiler Repair

[Rob Amstutz]

Hello. I just finished up my first year of burning with this old Wood Boiler in my basement. This is a steam/water boiler providing heat to my radiators. It does a great job. But this summer, I need to do some work on it. As you can see in the pictures, the cement (or asbestos) applied by the previous owner is falling apart. It appears to have worked for a long while. The seam itself is approx. 1/4in gap between the two cast iron tubes. On the other side of the seam is the interior of the boiler where the wood burns. My questions are this: 1) does it make sense to put some gasket rope in the seam before I apply refractory cement? Do I use 2000F rated? 3000F rated? Is there something else I should use?

Thank you for your time!