I'm trying to refurbish a tilt n trim unit from a 1985 Mercury 200hp which has been sitting for a while. I had to replace the motor on the hydraulic pump. At this point I'm just cycling the PTT using the two wires and a battery. Both the tilt and trim cylinders will run up without any problems. I've cycled everything several times, adding fluid while the tilt cylinder is fully extended. The system is now full and I don't get any burps of air when I open the plug. The tilt cylinder powers both directions just fine. The problem is the trim cylinders will not power down once they are extended. I can force them down by laying a 2x4 across them putting some weight on them while the pump cycles. Do the trim cylinders only retract via gravity/weight, or is there some other problem? A little help/advice would be greatly appreciated.
