Power tilt/trim issues

My 1999 50HP Johnson's power trim and tilt will only tilt up if I assist it with armstrong...mine
Then it will not stay in the up position....the motor runs great and tries to lift the motor and will do so somewhat......
Fluid level is full....bypass valve is set to the optimal setting......
Question...1) Can I replace the 'O' ring/s in the piston
2) Can I achieve positive results by replacing the hyd fluid with a heaver grade
3) Replace the whole unit

Thank you in advance
Mick

Living the American Dream on Anna Maria Island FL

They can be repaired but I would get a service manual on it before doing it. I've done it but always had a manual handy.

Boobie...thanks for your advice....where can I acquire a service manual...maybe online?
Mick

Yes on line or Ken Cook in Milwaukee WI.

Thanks Booble.....will report results
Mick