its a carbon ring assy. The carbon ring itself is forced against the steel collar by the accordian boot, inwhich creates a seal, so water dont seep into hull.
Take a look at the carbon ring and steel collar face, and determine if its cracked damged or scarred in anyway.
Might beable to loos'n up boot at thru-hull side, and smash as much you can toward engine, to tighten up pressure against steel collar and carbon ring, then retighten clamp....
