Given the rarity of Sea Marrow, and the little amount of Blight Fuel you get from it, namely needing to spend a full 3 units of Sea Marrow to make a single Blight Fuel, there is little reason to do such when wood is both cheaper and more plentiful. The default should be wood, not a rare fuel that you likely don't have when you first set up the Blight Post.
Likewise, I think the output for the other fuel types should be increased. 10 wood is a lot easier to get in almost all cases. It can remain at 10 for 1 output, and I would likely choose it even if the other fuel types were giving 3 or 4 units per unit in.