No trim under power

[BigAl331]

I've tried to find something about my trim problem and nothing. So here goes:

Tilt/trim motor will tilt and trim when there is no pressure on the foot by the motor under power. I can trim up as long as the motor is off or at an idol in gear.

Once it is up it will slowly go back down. When I lift the motor the only way I can get it to stay up I have to put the tilt lock in place.

I looked at the fill port and it is full, with the motor up and on the lock. If I take the screw out it will leak hyd fluid. The manual tilt screw had bubbly pink fluid but I think I bleed it out all the way.

Does anybody have an idea of what it might be? I really don't want to replace the entire unit just yet.