Yachting and Boating World forums: Outdrives doing there own thing?

As in previous posts I have re-engined and also put in new transom plates with Volvo duo prop drives, the 290/dpa type.
It would appear the hydrualics may not be conected correctly as to begin with they trimmed up but stayed up. However they did not have the power to trim out under power.
Ah ha I think! Look at the connections on the outside of the plate and they look the wrong way round.
So at the pump I cleverly change the unions so that I thought the high pressure pipe went to the correct end of the trim cylinders.
Great it works and trim works under power now.
So I come back the following day to find the outdrives have dropped and they are right down. I investigate and the drives come up and down but they drop the pressure so that under power ,trimmed up they gradually drop, and when at rest trimmed up all the way they trim all the way down over a period of time.
I drained the oil and filled with new ATF and wound the legs up and down a dozen times but still have the problem.
Cunning piece of rope now holds them up but looks a bit heath Robinson!
Any ideas????? This is driving me nuts. I am aware there are high pressure and low pressure pipes marked red and white to the trim cylinders but have not been able to investigate that yet. Sorry to bore all with questions and not stories of trips and anecdotes but I spend more time fixing than boating at the moment. Oh by the way the diesel issue not starting decided to cure itself before I could attack it. Thanks to those who made suggestions. Thanks in advance Simon.

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