Out of curiosity, find out what kind of props you have. Some are better under power than others. A Pearson 30 is about as representative a '70s design as can be imagined (like a Catalina 30, but less common), so I have a good idea of your hull shape. Let's assume you have an Atomic 4 or a Yanmar 18 HP as a motor. The fixed prop will likely be a 12 x 6 or 7 Michigan Wheel two-blade, with about an inch of tip clearance. The folder will likely be a Gori or a Martec two-blade of about 11 x 8. This means you will need more revs to get the same speed with the folder, but you will have slightly more thrust and a finer control at low speeds. This is desirable in docking and maneuvering. Allow me to give you an example: With a fixed prop, my "dead slow" in forward was about 2.6 knots. Consequently, I learned to shift into neutral and coast into dock, depending on winds blowing me on or off. I could, however, make 5.6 knots in flat water at half-throttle. At full throttle I could make 6.5, but cavitation and the noise made it hardly worth it.
By contrast, my "dead slow" with a Gori folder was 1.5 knots, and my stopping and reversing power were increased by about 25%. I also suffered less from prop walk, which meant that I actually used the engine MORE with a folder, because I could maneuver with more throttle control when I had options under 2 knots of speed over ground. I would also reverse off the dock instead of simply pushing the boat backwards with the engine in neutral and then hopping on amidships and throwing the tiller over until my bow had cleared and I could push the shifter into forward.
As for sailing, I gained approximately 1/2 knot in speed under equivalent wind conditions. I actually had to mentally shift my sail changing "bands" in the sense that I would opt for a No. 2 sail if the wind was over 12 knots for a daysail whereas I would have waited for 14 knots with the old fixed prop. The reason? I had less resistance under the boat and its sailing characteristics became noticeably livelier (as did its acceleration) in light-to-medium airs.
My experiences with a folder contributed greatly to our decision to purchase a feathering VariProp for our ocean cruiser...the pluses greatly outweigh the few minuses in my view.
But don't throw out the fixed prop...if the folder is damaged, you've got a solution one hour in a TraveLift can effect.