In case anyone needs it; here is the original drawing for the 335/325 keel cylinder.
  parker 335 hydraulic cylinder.pdf (595kb) downloaded 51 time(s).

Thank you for posting the hydraulic cylinder drawing, unfortunately the original manufacturer no longer make these.
I have recently removed the hydraulic cylinder from 325 Cascade as the cylinder wall has rusted through.
Does anyone know of a supplier or manufacturer of these, ideally with a stainless steel cylinder to prevent this corrosion problem in the future.
To remove the cylinder I had to remove the support bracket at the top of the keel box as the stainless steel pin securing the top of the cylinder has seized due to rust at the top of the cylinder.

Many thanks

Arthur Davies

For what they are worth, here are my thoughts on this :

1 These are fairly ordinary cylinders and a internet search should find you someone not too far away who can make you one.

2 I doubt if the expense of a stainless cylinder is worth it, Denso paste and tape will provide excellent rust protection on a steel cylinder for a much lower cost.

3 It is really important to take the cylinder out every year (perhaps every 2 years if you must) to renew the anode, deal with any rust, clean the lower 50mm of the ram and grease all the hanger and pipe fittings with lots of grease. After a few years practice this only takes 1-2 hours.

4 About once every 10 years the cylinder needs to be re built with new seals ( cost in 2023 was about £200)

Hope this helps

Martin
335/50

Thank you Martin for the benefit of your experience, I think one of the reasons for the cylinder failure on Cascade was the anode had been covered in denso tape but the cylinder had been left with a painted finish.
I have found a hydraulic cylinder supplier locally who is looking at it for me.