Years ago my plane, a VP-2, came with a de-Havilland 60"x30" prop. Its performance was so poor (produced max. 2850 rpm) it was dangerous. I went to Mangalore airshow and measured every prop attached to a VW there. They were about 56" max dia with far less chord and a flatter airfoil with max thickness about 1/4 of the chord. My prop had a Clark-Y type section with max thickness about 1/5 and a blunt leading edge. I attacked, taking 4" off the diameter, removing the brass L/E and savagely reducing the bulk. I placed an epoxy L/E and then had it sprayed white and with red tips and balanced it. When I ran it, tied to a tree with a spring balance, I found the static thrust had reduced from about 150lb to around 120! Well, time to run it along the strip to explore the result. I was shocked to find that the revs had increased to 3600 and it accelerated like a racehorse. I then committed to the air and found that the miserable climb performance had improved to 500fpm. It cruised at 3200 /60kts.
I believe that the old prop was acting similar to a fan. It moved more air at zero airspeed giving a thrust figure of about 160. However, the purpose of a propeller is to accelerate the air to a high velocity. It therefore produces more reaction force to the airplane and an increase in performance. The engine was obviously producing more hp and the prop converted this to a more energetic airflow.
I'm not trained in physics so am unable to explain in more technically precise language. Simply my experience. (Don't be afraid to experiment, most satisfaction comes from positive experience {or, as Facthunter explains,"Never stop learning."}) Don