Many thanks Martin, I found your drawing of the ram. My ram won't hold hydraulic pressure so the keel is either up or down on my drying mooring! The long hose from the reservoir sprung a leak the day I launched last week and I think caused the seals to burst with the influx of air. You couldn't see the damage to the hose as it was to the bottom of the hose, but I could feel it. It was directly below the hole in the keel box cover, so exposed to sunlight and water. But why to the bottom and not to the top of the hose? Very strange. I have replaced the long hose which although a difficult job, wasn't as tricky as I thought it would be. However, the ram jets oil through the breather and won't lift the ram more than half way.
I am taking the boat to the marina tomorrow for lifting out.
I will take the ram out and take it to a hydraulic shop for them to investigate. I will see if I can get a new one. It will probably be very expensive so hopefully mine can be reconditioned.
I have learnt that the long hose should be replaced as part of a service schedule, even if you see no damage. The old hose was stiff and awkward and a little brittle. The new hose more flexible and easier to handle. Mine was 22 years old, so I suggest replacing it every 12 to 15 years. It cost £220 to replace and took about 3 hours in total. I might write an article about it for the newsletter.
Mike