Bear:
Please post a picture. Does your 222 have an access plate at the centerboard pulley ? Not all have the access plate. See attached examples of 222s with and without access plate. Is the "dark gray hard material" you refer to located under the cabin step?? Not sure what the original non-PVC material is, but there are other solvents to bond PVC to ABS et al. Check at the plumbing department- and take a sample of original non-PVC material along.
Mich222