Honda BF35A-BF45A Outboard Motors Shop Manual., Page 418Get this manual
2) Apply ATF to new O-ring, and install it on the free
1I FREE PISTON
3) Apply ATF to new O-ring and install it on the piston rod
4) Apply ATF to the inner wall of the cylinder5) Install the free piston in the cylinder taking care not to
damage the O-ring, and pour the fresh ATF on the free piston6) Install the piston rod in the cylinder taking care not to damage the O-ring7) Push in the piston rod until the free piston end aligns