Brunswick/Mercruiser chain driven stern drive

I found this patent of a chain drive system for a stern drive from Brunswick:

http://www.google.com/patents/US4925413

Does anyone know what happened to this patent? Why didn't it hot the market? Did they run in to some problems or was it something else that ended the development?

Thanks everyone!

 

It has a drawback in hydrodynamics in that it requires a much "fatter" vertical leg than the vertical shaft variety. The idea was probably to increase torque capacity, but the added complication of an extra set of gears for a reversing mechanism and the increased resistance would be enough to kill the proposal.

Compared to the slim profile of the leg and the torque capacity for a double vertical shaft configuration with its simple reversing, I can't see one single point in favour of a "chain leg".

 

If you search gb.espacenet.com for marine propulsion systems you will see that Brunswick owns the weirdest patents. For decades they have bought ideas to keep others from entering the market.

 

proving there is more money in selling an unproven idea than actually selling the product