1972 Evinrude Starflite 100 HP Spark advance rod

[72muskie17]

I recently bought a 1972 Crestliner with a 100 HP Starflite Evinrude. The motor has been sitting for quite some time, but I've done most of the preliminaries when I first started it and before I mounted it again. After some broken selectric controls issues, I was able to get it running pretty well. However, now, after it warms up, the spark advance rod locks up. I'm able to repeat this with it idling in the driveway. I'm going to pull the flywheel and see if anything jumps out. Any advice?
I appreciate the help