|Take the timber top of case off and use a block and tackle at the top and base of the keel to remove it. This way you dont have to take the boat off the trailer to access it. |
The other way is to roll the boat over in the shallows and remove the keel bolt from the inside and slide the keel out from underneath. Caution, fill the bolt holes before you let the boat back up. Else it will fill up.
When you replace the keel remember to use plenty of silicone on the bolt and top of the case.
As far as the keel knocking is concerned, if you find a succesful way to prevent, you will make a lot of money.