Thank you all for taking the time to give me your advise and feedback.
The research I have found is that this motor is an replacement for one designed to pull lobster traps out of the water (not kidding).
The link below suggest that the third connection is for reverse. Not sure I trust this...
I am really enjoying this forum as there are a lot of pretty great ideas and information here. I am building my son and electric gocart. I made the mistake of purchasing a motor before buying the controller. The motor I purchased has little information on line to let me know what type of motor...