1989 60HP merc TRIM MOTOR FAULT

Hi everyone, I've just replaced the trim/tilt motor and it won't drive the motor any lower than approx 35 degrees, above this angle it will raise to the end stop and lower back to approx 35 degrees then stall. If I release the manual release screw the motor drops to the vertical position under its own weight. I drove the top pin back out and operated the motor again watching the hydraulic ram extend fully out and back in again with no problem. The battery is fully charged, I've used ATF to top up the pump reservoir. Once it stalls it has to be manually tilted back into its operating range.

I'd appreciate any feedback.

Fixed Bled all the fluid out by disconnecting ram, removing fill screw and cycling ram in/out until no more fluid was coming out. Refilled, tighten screw, ram down/up, check level, refill, repeat sequence. Each time screw was released air was purged from the system. I suspect I had an air lock somewhere, all sorted now.