trim and tilt problems with 830159T unit

[bcs95tbobber]

Need help in determining what needs fixed or rebuilt on my power trim and tilt # 830150T. Problem is it goes up and down but will not stay up, bleeding down to lowest position. Checked fluid and top off. What should do next to trouble shoot.

Also the motor and switches all work, i believe it is the cylinder or what stops it valve etc. If the cyclinder or valve need rebuilt what are the part numbers I would need?

Any help would be appreciated...