Regarding the tentioning thingy. West Marine still sells the tensioning handle. I bought an extra one for my boat a few months ago. The black plastic unit sell for aroung $10.88. Check out the following email site ( AUTOHELM 3000 - Froogle
Secondly, I have had similar problems with my autohelm 3000. I purchased a remote that had four pins and my control unit has five.
The motor you purchased will most likely not work with the control unit you have. My unit has the two wires, brown/blue. I know for a fact as I have had to do some tightening of loose connections. I also found out what happens when you reverse the two wires. The motor works but 180 degrees opposite of where you want to go. It made for a quick U-turn on the water. I am not sure you can work around the other two wires. I tried to find a wiring diagram for the autohelm but was unsuccessful.
I know you can still get the working directions for the unit at Raymarine. It does not have any info on plug pins or two vs. four wires for the motor.
I was able to find a guy that had the four pin remote and have made arrangements to trade his five pin for my four pin. He sounded like he knew what he was talking about and said you have to understand it is a British thing? Don't try to figure it out?
Anyway, you probably have a motor that will not work with you control unit. You now have to find a new control unit. Happy hunting...
If you want I have the guys email. He has access to autohelm stuff. If you are interested I can send you his email address.