Some items I would add for the OP... The propellers you are dealing with on the Seminole are not termed "controllable pitch" that is yet another type of propeller and some were in use as essentially an interim step in the evolution to the "constant speed" propellers used on most airplanes today. Controllable pitch propellers are a pain in the butt, like turbocharger installations with manual wastegates... The constant speed propeller control system uses engine oil as hydraulic fluid. This negates having to make use of a separate, dedicated fluid supply system for the propeller. However the engine oil pressure is insufficient for the purpose of moving the propeller blades in a dynamic situation. To that end propeller governors also incorporate a small oil pump to greatly raise the fluid pressure in the system. For practical purposes the constant speed system in the twin works much the same as that in a single, except backwards as that is the easiest way to "design in" the feathering capability. When you lose oil pressure in a single engine airplane a constant speed propeller will default to low pitch (high RPM) in a multi engine airplane the default is to high pitch, toward feather (low RPM)