Indeed both aluminum, and very fragile. Especially trying to get it moving is dangerous as you are tempted to use the "teeth"on the other side. However we got them loose again, but do not ask me which treatment finally helped. We used everything available from heat to soaking it in oil and other fluids.
Most of time it's not just one thing, but a combination. Glad you got it apart okay. I'd heed the advice to run a tap and die over everything to clean out and clean up the threads. And make sure to coat them in anti seize or grease when you re-assemble everything
Makes me think I should take my spreaders apart and clean them just for good measure.
The list of **** I need to do to my boat in the spring is horrifying.
