Capilano Steering Problem

[reiner]

I guess most hydraulic steerings are pretty much the same?
We got twin steering with two Seastar 1250V pumps and a Capilano ram pushing the rudder. This is all pretty new to me, I like tillers.
Anyway when I try to steer a straight line I have to keep correcting to port until the wheel does a full turn in about 15 min. My guess is the fluid leaks somewhere from one side to the other makes the system loosing pressure.
I pulled the 1250V pump apart and got all new o rings plus replaced all the fluid in the system. No change to the behaviour . I rang some hydraulic people and they told me that a 23 year old system is not worth saving and fit a new hydraulic steering. They would say that.
I didn't pull the ram apart and start thinking the problem could be there because I find both wheels slipping.
Has anybody any suggestions where the problem could be? Or should I listen to the hydraulic people and replace the whole system?
Happy new year to all
Cheers
Reiner