Evinruide 120 HP Rebuild or Not?
The quality of the rebuild will be the key to having a reliable outboard.
The one issue which can haunt that vintage of engine is pistons. The pin which locates the piston rings can come loose and allow the rings to rotate and catch in a port. It is possible that's what happened to fail it.
It is very risky to rebuild one of these engines without replacing all the pistons, rings.
The condition of the cylinders is the other question. If they are not badly damaged or worn. Many times they can be clean, honed and reused without boring oversize.
All of this said you'll have to way the cost of the rebuild vs the cost of another engine. Used engines are available.
Good Luck Highthrust