Some details
Replacement of any sheave, first measure pin diameter, this will let you know what sheve you can use, second halyard diameter, third, width of sheave, and last diameter of sheave, with this data, go to west marine, check out shaeffer and harkin and any other hardware co. normally in the rear of these books, if you want derlin bearings, or an aluminium sheave, or what ever, check them all out, Your old block may be a merriman, and to use it you have to grind off one side of the pin, to release the sheave,which can be replaced with a 1/4"-5/16" or whatever bolt and locking nut, I went for the derlin bearings in any case 1/4th the price of a new replacement. if they don't have it in stock, order it, your sheet blocks and other blocks s/b checked out too.
