BF 225 tilt-trim won't trim out under load

My 2002 225 A2XA had developed a trim problem that needs a diagnosis. It will does not want to trim out when the engine is under a load below planing speed. If I pull the engine to neutral, the trim seems to work properly. The fluid level is full and the unit makes no unusual noises and has no leaks. The tilt-trim works fine out of the water. The only parts on Boats.net that I see that might help are a $780 pump or some sealing o-rings. Anyone else with similar issues and how did you solve it? Is there any seal kit available that would help? TIA!!

Before tearing into the hydraulics, I would be absolutely sure the electrical connections are in top notch condition. A corroded connection may not be allowing a full 12 volts to get to the motor, which would show up as poor performance under load. Check the plug from the tilt-trim motor that is inside the cowling - they often get soaked with water. Check the connections on your tilt trim switch(es).