They're unique. Originally designed to power fast torpedo boats during WW2, three of these powerful and compact engines would churn out plenty of power for the boat up to 50 kt.
https://everythingaboutboats.org/napier-deltic/
They're still in use by our UK navy. Nine minesweepers still on active duty.
They're still in use by our UK navy. Nine minesweepers still on active duty.