Well I am not sure about all of them but I know some had Man Diesels, I am sure they used different brands because how many they made and being a time of war. I m not sure exactly how the shafts are hooked up I know they arent a strictly diesel electric drive because when surfaced they could go so much faster than when submerged. I assume they had a clutch on the engine so when they surfaced they could engauge the diesels and shut down the electric motors.
In a normal diesel electric drive. The engines arent hooked to the shafts in anyway and just run a generator, then electric motors turn the shafts. A lot of cruise ships are diesel electric drive. I have been on a couple. They are nice for manuvering. When you have a diesel hooked straight to the shafts you have a min rpm when you engauge the engines. On a diesel electric drive there is no min. You can put 1 rpm on it if you want.

Diesel electric drives are cheaper and faster to make also. You dont need a reduction gear which is the mose expensive part of the ship. A lot of the old liberty ships used electric motors for propulsion except they used a boiler and turbine to make electricity.
I am not sure if there is anything in there that you wanted to know but if you want to know more just ask.
A good book about uboats is Iron Coffin by John Mannock. He is pretty accurate unlike a lot of the other ship related books I have read.