Dual levers are normally only used when you have two stations. I personally do not like two levers - too much to worry about when backing on a fish, or trying to avoid hitting a dock, etc. IMO, stick with a single.
Check your cables, willing to bet they're toast... that's the problem 99% of the time. Order some of the teleflex high end cables (can't remember their name), it'll be good as new.
If however the cable is good, could be you have a problem with the shift linkage inside the motor. Once you disconnect the cable to test, you can manually actuate the linkage by hand to see if that's it.
