Yamaha F100B F100C Outboards Factory Service Manual, Page 296Get this manual
Bracket unit
WARNING
After tilting up the outboard motor, be sure to support it with the tilt stop leverOtherwise, the outboard motor could suddenly lower if the power trim and tilt unit should lose fluid pressure7Remove the reservoir cap 1, and then check the fluid level in the reservoir8If necessary, add sufficient fluid of the recommended type to the correct level
NOTE: Repeat this procedure so that the tilt ram goes up and down four to five times (be sure to wait few seconds before switching the leads) The sound of the power trim and tilt motor will change when the tilt ram is fully extended8Check the fluid level again when the tilt ram is fully extendedAdd sufficient fluid, if necessary, and then repeat step 7NOTE: Repeat this procedure until the fluid remains at the correct level