Re: 69 merc 1000 trim
Interesting. I was going to say that your piston seals were worn, but the opposite effect would be expected. With worn seals it wouldn't want to trim down fighting the incoming force of the water whereas it would easily move with the water and trim up getting the prop out of the water.
Obviously there is not much resistance on the trailer. Only thing I can think of would be a defective up trim relay. You have 2 just alike and you can just swap the up for the down and see what happens. If the problem follows the relay then you have your solution.
Mark
