Yamaha F100B F100C Outboards Factory Service Manual, Page 256Get this manual
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4Remove the manual valve 2, and install the up relief fitting and hydraulic pressure gauge 4, and then tighten them to the specified torques
7Reverse the PTT motor leads between the battery terminals to fully extend the tilt ram and trim rams, and then reverse them again to fully retract the ramsNOTE: Repeat this procedure so that the rams go 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 rams are fully extended If the rams do not move up and down easily, push and pull on the rams to assist operation8Check the fluid level again when the rams are fully extendedAdd sufficient fluid, if necessary, and then repeat step 7NOTE: Repeat this procedure until the fluid remains at the correct level