This post brought to mind what I saw at the Mercedes museum in Stuttgart.

One of the very first internal comubustion engine boats is in the museum. Daimler or Benz, I don't remember which, built the boat and disguised the engine. The whole idea as I remember was the novelty of being seen in a boat that seemed to move with no visible means of power. I can't remember the story behind the engine disguise.

If I remember correctly, this may have been the first powered boat of it's type.

It seems that the diesel Benz would be an ideal marine engine.

Good luck,