Masthead sheaves, replacement

[Sailor Jim]

I own a 1997 Catalina 28 MkII tall rig. The topping lift is off its sheave (port side, aft) and jammed between it and the masthead box. This probably means a broken sheave; I intend to replace all four of them. Through binoculars, the forestay and aft stay appear to attached to the masthead box. In addition, I don't see any obvious way to pull the sheaves without taking the masthead box off.
Can the sheaves be replaced by climbing the mast and pulling them from the masthead box? Or, does the mast need to be brought down, the stays removed from the box, the box pulled and sheaves replaced?
Thank you,
SJ

 

[Alec]

Jim,
There should be pins that go thru the masthead box and the sheaves that are held in place by cotter pins on the outside of the box. You do not remove the masthead box to remove them and can accomplish this by going up the mast. Catalinadirect.com has the sheaves. Suggest you get the metal sheaves, especially for the main halyard.
Alec

 

[Shell]

See http://www.sailthehudson.com/Refitting Sea Fever.htm when I re rigged my boat.
I replaced all 4 sheaves with metal bearing load sheaves.
Good luck.

 

[tommays]

While i guess youcould replace them in place

When i re-bushed mine over the winter there was a lot of fighting to get out the pins and a lot of risk of droping things into the mast even on the ground

 

[Hermit Scott]

I was just up the mast the other day and mine look like phenolic sheaves. I can't believe they lasted 30 years. I want to replace mine also. What is the best replacement material, aluminum with bronze bushing, or stainless with bronze bushing?
Jim-mine can be replaced by knocking a pin through the mast head that the sheaves ride on. I would tape them up to a small rope tied to you because if you knock the pin out you are likely to drop them down inside the mast.