You can see it on the vines atop the building at the far left of the island.
However, the only way to get to the Mech Crank is to use the Living Quarters key, which is in the Research Lab at the far right of the island (essentially solving more than two-thirds of the quest). Once you recover the Mech Motor from the Lab, and return to go through the Living Quarters for the crank, only the monster plant sequences are left to solve on the island.
(see related solution)
You have to get the mech crank and the motor.
You can get the mech crank at living quarters in Zack's room ( go up the ladder and exit the room and walk across the vine and pick up the mech crank)
find the mech crank and mech battery
The unfinished Mech that Zack was working on is in the garage next to Sully's. You need the Mech Motor and Mech Crank to finish it.In the garage next to sully's shop on the left side of the island.
The Mech Walker is the key to entering the storeroom and defeating the monster plants that are active there. Once you finish the Mech with the Motor and Crank, you can attach the Weed Whacker attachment and enter the door at the far left of the island.
Along with the Mech Crank, it completes the Walking Mech that is in the garage next to Sully's. To get the Crank, you have to go through the Living Quarters to reach the high vine at upper left.
Go left along the vine and pick up the Mech Crank. Along with the Mech Motor you recovered from the Production Zone, use it to finish building the Mech walker.
you go in it
There are no windows that open inward on Steamworks Island. There is a skylight in the City Hall that can be opened with the Multi-Tool. You go out the hatch above Zack's room in the living quarters, to reach the Mech Crank on the vines.
Where you find gears on the island, you will normally use the Multi-Tool which you get from the Cantina at the start of the island. To turn the gears at the cantina, use the crank at bottom right. To start the elevators in the annex (with the Mech), just exit the Mech to turn them on.
You cut the weeds blocking the door of the Storeroom far left of the island) with the Weed Whacker. The weed whacker is in Captain Ziggs' room atop the Hub, and must be attached to the Mech Walker (in the garage next to Sully's). Finishing the Mech requires the Mech Motor and Mech Crank.
in your bag there is a mech crank in it