The cone comes off easily if installed correctly, which it isn't by most "marine engineers".
For our 120S-E, that means:
Propeller cone 70 Nm - grease splines first
Cone lock bolt 20 Nm - with Loctite on threads
70 Nm isn't that much for a thread that big, so many mechanics instead apply the good old "as tight as you can fucking get it" principle, creating a problem for the next person to remove the cone and potential damage to parts.
Your standard torque wrench won't fit the cone, but a simple spring loaded luggage scale at the end of a lever will - the math is easy, 70 Nm is about 7 kg on a 1m lever - adjust for the length of your lever.