My 1992 Seaswirl Cuddy has the OMC Cobra 4.3L sterndrive. The trim system works OK by raising or lowering the sterndrive when underway but I am having to readjust the trim often. When I tow the boat on its trailer, I always install uplocks. The other day while winterizing the engine, I did not install the uplocks and the drive bleed down to a near vertical position over night. The trim system appears to have an interal leak that is allowing the trim cylinders to bleed down. Where should I start in order to fix the bleed down problem? 