Rig said:

A plumbing license wouldn't normally allow you to work on boilers, that's a whole different thing that requires a special license.

Yes, the boiler work would require a steamfitter, with appropriate license.

Plumbing is simply not that way in any state I've worked in, and it isn't that way in Ohio. (*)

If that statement is true, it's clear you have not worked in Indiana, then, Rig, (and I doubt your statement, even as to the other states).   I'm a court reporter, and I am called from time to time to report hearings before the Indiana plumbing commission. One of the most frequent situations is where someone is hauled in for practicing plumbing without a license, or acting as a plumbing contractor without that license, or where he's failed the plumber's examination and wants them to regrade certain questions, or where he doesn't have the requisite experience working for a licensed contractor to be qualified to take the exam, or is practicing with an expired or even a revoked license.

(*) It looks to me as if you just make these things up as you go along.

Dave Oesterreich