It has been done.  That variation was a neat system that used a single roller clutch as the primary drive component.  It was a relatively simple drive arrangement:

Biomechanical efficiency is similar to rowing in calm conditions so in that regard it is not as good as pedals.  As with rigger rowing, more power can be delivered over a 5 to 10 minute interval when working anaerobically compared to pedals.  It has the advantage over rowing that it is a considerably more constrained body action.  Hence it does not require the fine muscle control and long periods of muscle training that rowing requires to use oars at high efficiency.  

One inefficiency of rowing I did not mention is the speed variation compared with the almost continuous thrust of pedalling.  That it itself introduces losses compared with steady speed.  With propeller rowing the losses in this regard are even higher because the prop is spinning through the water with significant losses compared with oars moving through air on the recovery stroke.  Obviously the comparison is closer if the oars are pushing through a head wind. 

The inventor of the this propeller driven system helped me develop the pedal powered swing arm system I used on my V12 boat:

It has twin roller clutches and power is applied more continuously than rowing.  Warren also converted the boat in the above photo to pedal powered swing arms.  At the design speed the swing arm system  has slightly higher biomechanical efficiency than cycling but only in a narrow range of operation.  It is a much sweeter  action than the Hobie pedal system - very natural treadle action you may have experienced in your first toy car but the leg stroke is not mechanically limited so the individual can choose the preferred length of stroke. 

Rick

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