Those ships are powered by baby chickens.

First they load up the tanks full of baby chickens. The chicks travel into a conveyor belt where a long row of old women pick up the chicks to if they are male or female. The females are grown to make more eggs. The males are tossed into the intake. The males are then mixed with air and tar and then injected into the piston at high pressure. Once top dead center is reached, a spark drivers the pressures to hundreds of PSI and as much as 800 C. The chicks have been known to survive up to that moment.

If they can perfect chick injection they will try more compact fuels like puppies, crocks, whales, baby elephants, the homeless and or orphans. They might end up stuck with birds so they might try just eagles. There are enough of each eagle to push the boats a good two or three miles!