I was reading a forum item about water up the rudder stock tube. This was something I had never considered or been told about although on very hard reverse on my NB I would get water up the tube. I just put this down to poor design because of its age. When the water came up it just ran off the self draining read deck, but on this boat it's going to go into the engine room bilge.......... Not good.
As I hadn't considered this I needed to work out how to retrospectively fix it. Much head scratching and I came up with this idea.
I disassembled the rudder, ram and removed the stock.
I then slid a length of PVC pipe over it having first coated the shaft with silicone grease.
I reassemble the rudder and stock then filled the gap between the stock tube and the PVC tube with closed cell expanding foam.
Once cured I trimmed off the excess.
I think this will solve the problem.