Please elaborate on what to specifically look for. Just had the gear oil changed and since I was having to run on only one engine I did a pre flight the day before as I didn't want to blindly pull off the dock already down one engine. Started fine, warmed it up, and when put into gear very sluggishly moved forward. Same for reverse. Called mechanic and he sent out his seasoned tech, great guy. Start for him and he immediately yells shut it down. Filter housing leak. Turns out the tech who did the work installed 2 gaskets, not just the one correct gasket. They fixed and took apart the other side. That had only the one correct gasket. Wonder if the gasket got damaged and this is enough of an air leak to allow pump to drain and loose prime. It sat for 6 weeks while in the yard.