I have o4 trim pump with XR drive package.It works fine on the trailer an when not under acceleration.The pump has the new type fittings so you cant hook it up wrong.If I try to raise the drive while under load it wont move.This is in an 05 290SC Velocity with a 525 motor.Any ideas?

Check your ground connections....some trim pumps can be very ground sensitive. Make sure connections are clean, free of paint, and are tight.