311 keel knocking

I have spent much of the last season with my keel knocking, and have tried raising and lowering the keel with no improvement. The keel lift mechanism is fine, therefore I have decided to replace the keel pads, (x4) and adjusting pads (x2) during the winter lay up to resolve this problem.

Has anybody carried out this excercise before, and can offer any advise. (I have already removed the adjusting pads (x2) - they were locked solid in the stub, so no adjustment possible !!)

Any idea's or advise would be much appreciated.

regards

Graham Smith