Re: 4 blade vs 3 blade props, is this a way of over-propping?
Overproping is the intentional "overloading" (the engine will no longer be able to reach max rpm ) to increase the engines efficiency at a lower ,power setting.
Adding an extra blade is not the best solution as 4 blades are not as efficient as 3, if the 3 has sufficient blade area.
For a cruiser who understands the process a cruising prop can save large amounts of fuel and extend the engine life.
For the uncomprehending it can harm the engine.