Wow, this thread really took off before I had a chance to respond.

daven,

I never claimed that a .52 (fifty-TWO, not .56) 4-stroke had 50% more power than a .46 2-stroke. You claimed that your .46 2-stroke can swing a 12x4 prop. I'm not arguing that point, because I've seen it done.

However, that 12x4 prop loads the engine down and drags the RPMs outside the optimum power range. Most .46 2-strokes can't swing a 12" prop at more than 10,000 to 11,000 RPM. Most .46 2-strokes are capable of producing much more power in the 12,500 to 14,000 range. You are not getting optimum power from the engine by loading it down so much.

Power is a function of torque and RPM. Given the same RPM, the engine that can swing more lumber has more power. At 10,000 RPM, the .52 4-stroke has the edge on power because it can swing a propeller with 50% more pitch. Because propeller load varies directly with pitch, 50% more pitch means 50% more power is required. Of course, this is all purely theoretical, and ignores many real world factors, much like the F-F-F-Four Stroke page does