Subject: How do I calculate the amount of energy produced by a water turbine?

This turbine is fictionary, since it's an invention for a school project.  
The boat using these side-mounted turbines is of 600', 300 tons and 
going at an average speed of 17.5 knots. Before I determine the size of 
this turbine, I need to know if there are formulas to calculate such things 
as:
- How much energy would be produced by water turning the propellers in the 
turbine, for an extended period of time
- How these turbines will affect the braking of the ship
- How much thrust they could generate

Just wanted to know if it was possible.  Thanks

Re: How do I calculate the amount of energy produced by a water turbine?