2265 - Friction Lock Kit
The friction lock is the part that holds the drive train in place and allows it to pivot up and down. You can set tension by adjusting the knob below the Friction lock on the "Hub". (Illustrated by the blue arrow).
Replacing the Friction lock requires the removal of the Drive Train, replacing the Friction Lock, and then install the Drive Train back.
Hydrobikes with Knob (2014 and later models)
Simply take the Knob and bolt right off (bottom rear of metal frame as above) which will ‘spread’ the round rear hub and make it easier to remove the existing drive from the left side of the bike ... friction lock pulls over the sprocket on right side.
Hydrobikes Models Prior to 2014
The procedure is straight forward and the instruction sheet link is below.