2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 194Get this manual
Tilt cylinder and trim cylinder NOTE: Repeat this procedure so that the ram goes up and down four or five times (be sure to wait few seconds before switching the leads) If the ram does not move up and down easily, push and pull on the ram to assist operation3
8Check the fluid level when the tilt ram is fully extendedAdd sufficient fluid if necessary
A S6D87470
Installing the power trim and tilt unit
1Fully tilt the outboard motor up, and then support it with the tilt stop lever 1
Bleeding the power trim and tilt unit (built-in)
1Fully turn the manual valve counterclockwise
S60C7975