Thanks in advance to anyone who can help a Mercruiser novice solve a trim problem:Equipment: 1977 Sea Ray Cuddy with Mercruiser 888 (Ford 302) with Alpha outdrive; 3-button trim system with Arco trim pump motor;Problem: Trim works perfectly going up, does not work at all going down (and I've tested this in the water and on a trailer, with the engine running and without). Trim motor itself appears to be working OK (judging by the correct sounds it makes) in both directions. What I've done so far: cleaned all electrical connections, made sure that pump is full of hydraulic fluid; Possibilities: I've read that this model trim system has something called a 'reverse lock valve' that is in-line in one of the hydraulic lines. 1. Would a malfunctioning 'reverse lock valve' cause the trim to only operate in the "up" direction??2. Is it possible that there is something wrong internally with the pump that would allow it to push hydraulic fluid out (and thus make the trim go up properly) but not pull fluid back in and allow the trim to move back down correctly? 3. If the pump is malfunctioning internally, can this be repaired or would it require replacing the entire pump mechanism?I've tried to provide as much detail as I can, but please post questions if it will help someone out there give me some advice on what to try next.Thanks a million!!