Had problems with early eighties hydraulics on merc 90 inline.(tilt motor inside the boat)Motor became unreliable so mechanic replaced with exchange unit. Also replaced seals on both trim cylinders as the leaked. Problem now is that the engine will sink it's full travel in about five minutes. Can't see any leaks, all conections are good, not losing oil. If this was air in the system wouldn't it just be "spongy" as the air compresses. I can get the boat back to the mechanic but it's a fair tow. He says this system is self bleeding. My manual says not.Iv'e bled these systems before and i don't want to introdude air into the system if this is not the problem. Any advice.
