1. Going internal from external halyards. I'm planning to make that change on my boat. I have the mast down and started looking at it and thought it would be an easy swap. Then ran into a comment by another owner who had done exactly that several years ago and was very happy with the change and had experienced no problems.
Yes there are potential snags inside the mast and potential to tangle with the wires that go to the masthead and steaming lights. I looked up the bottom of my mast with a spot light and binoculars and the wires are wrapped together and should not be a problem. Will just have to be careful droping the halyard down the mast to make sure it runs free.
Whether it works for your mast will depend on how the masthead fitting is rigged. For me it was easy. The masthead had four sheaves in two pairs. Two side by side on the front of the mast and two side by side on the back. The original mainsail
halyard ran up the front of the mast, over the front starboard sheave, over the inside of the mast, over the top of the aft starboard sheavej, then out and down the back of the mast. Jib did the same but in the opposite direction on the port side.
So to go to four halyards, instead of going over one sheave, over the top and down the other side I just go over one sheave and down the inside of the mast. I will have to cut exit holes in the sides of the mast and fish
the ends of the halyards out but shouldn't be too tricky.
If you have a similar setup you should be able to convert. You might have just large sheaves right in the middle of the mast which would make the changeover much more problematic.
2. Noisy sheave. Is it a noise
like a squeaky hinge? Lube it. If it's rattling then the sheave or it's shaft may be worn and require repair.
Does the boat have a spinnaker
halyard? Since you have only the main halyard I would want to find some way to rig a safety
line in case the main halyard slipped, broke or in some way let me down (pun intended
). If you have only the main halyard I would highly recommend rigging
a line around the mast with some type of sliding knot
(would a Prussic knot
work on something with that diameter?) to a harness to catch me just in case the main failed.