Yes Carryfast, if you google you can find examples of petrol powered slow boats and diesel powered speedboat. But unlike you, I do not rely on google, but actual hands on knowledge.
We have discussed the MTB/E-boot choice of engine already. The germans had a developed diesel engine. The British did not. The E-boot was also nearly 50% longer than the MTB.
And what was the engine of choice of the U-boots?