The hovercraft (hoverboard) is powered by manure. To get into the attic of the mill, pull the rope inside to unlock the gears. Clmib on the windmill arms and turn them counterclockwise to open the roof dome.
The hovercraft runs on manure.
In Astro Knights Island on Poptropica, the fuel for the hovercraft can be found in the fuel canisters located next to the dock where you first arrive on the island. You need to collect the fuel canister and use it to power the hovercraft to cross the toxic swamp.
The fuel rod powers the saucer Excalibur. The hovercraft runs on manure.
The hovercraft takes you out to the crashed saucer Excalibur in the mud swamp. To repair it, you will need a new green fuel rod. (see related question)
Go to the mud and you'll find it there. As soon as you fuel it, it stays right there in the swamp.
To obtain manure for the hovercraft fuel in Poptropica's Astro-Knights Island, go to the farm on the main planet and explore the barn. You will find an item called "Excrement" there which can be used for the hovercraft fuel.
Once you have the hovercraft from the attic of the mill, you can bring the fuel rod to the saucer (Excalibur) and use it to launch into space. The cordinates are X-56 Y-52.
You need to get a replacement for the broken Fuel Rod and the coordinates you will need to enter in the flight controls. (see the related questions)
The fuel rod replaces the damaged one on the saucer Excalibur, which is crashed in the mud swamp to the right of the Mill. Get the hovercraft from the mill attic to reach it. (see related questions)
No oil on Astro Knights Island. The hovercraft runs on manure, and the crashed saucer Excalibur needs a replacement for its broken green fuel rod. (see the related question)
You have to get the fuel rod
While the hovercraft built by Mordred runs on manure, the saucer is advanced technology and its green Fuel Rod is empty. You will need another Fuel Rod. (see related question)