Yesterday after working fine for most of the day I noticed that the UP trim on my 5.7 Duo prop was no longer functioning. At idle speeds it seemed to work just fine but under load did not want to trim bow up. If I started out with some UP trim, it would hold position; and it would trim down just fine. Seems like the fluid pressure is not adequate to move the drive under load, but will tilt for trailering. Any ideas? Is there such thing as a "weak" pump? I suppose maybe internal seals allowing leakage under high pressure maybe? Not sure how to start my trouble shooting.