I have a 2000 Johnson 115. (VL, I think) It's the white version, long shaft. If I trim or tilt the motor up, it lowers itself back down within a minute or two. The motor and fluid level seem fine. Response both up and down is instantaneous. It simply won't hold position. I've attempted to check the manual release screw, and it seems fully tight. I don't have good visibility of it, due to the hull layout. Also, I can't pull the ptt unit off without removing the engine from the boat. No clearance to remove the lower ptt pin. I don't see any sign of an external leak. Any suggestions before I try to find a motor lift?
