1995 Yamaha Pro 50 Trim/Tilt problem

I recently purchased the Yamaha Pro 50. I noticed that the motor when up on trim/tilt will slowly go down over time. The tilt/trim works fine but will not stay where it is left unless I lock it all the way up.

Any suggestions on this problem would be greatly appreciated.

Thank you.

[boats.net]

Check the manual release screw is tight. It may have to be rebuilt to solve problem.