A friend has a 93 Larson with a Merc 350 and a Bravo III out drive. The hydraulic trim for the outdrive goes up and down just fine, unless you bring it all the way up. If you do that it won't go back down on it's own. To get it down, one person holds the button activating the pump in the down direction (it can be heard running) while a second person hangs/pulls down on the outdrive. With that assistance to help it move the first inch or so, it then operates fine all the way down and up, except for if you bring it all the way up again.

I imagine someone has seen this before. Thanks for everyones help.

Maybe low on fluid. Does the pump change tone. Corrosion build up in the cylinder end cap will also hinder down travel but usually the whole range. If you remove zinc and visually check cap where rod protrudes look for seal and scraper jammed with corrosion and scratches on rod.