I was able to visit the boat for a couple hours on Thursday between snow storms. After I replaced a number of snapped lines on the cover, I fooled around with the traveler lines and took a look at the sheaves as discovered and reported by stevemitchell on March 9. I found my sheaves to be in better shape than his, but with the 4:1 purchase there was too much resistance in both the line and in the sheaves. The old line line appeared to have been a 3/8" line that had swollen to about 7/16" with age, and the replacement line I installed was about 3/8" double braid polyester, something like Sta-Set. But it looks like the sheaves are really made for 1/4" line (or perhaps 5 mm, 1 mm smaller). I tried some 1/4" line I had on hand, and it seems to be the maximum size that will comfortably fit the sheaves. Also, the line needs to be very flexible, as the sheaves are small with a tight turning radius for the line (as alluded to by cymeyer above).
Some of the sheaves spun fairly freely, and others turned easily but would not spin, even in the 40 degree weather. I found some replacement sheaves and bushings on eBay (size 2 Lewmar), but I'd really like to upgrade to ball bearing sheaves. The 2014 and 2015 Lewmar catalogs for spares show an option for size 2 NTR traveler parts that have ball bearings, but I have not yet located a source. I will have to call Lewmar and see what they suggest (see Lewmar parts 29432372BK and 29472076BK). The Lewmar traveler upgrade kit contains only roller bearings. Lewmar part 29472012BK appears to be something like the original sheaves.
I think Lewmar upgraded to the ball bearing sheaves a couple years after my boat was made in 2000. The 323 was the next model and its parts catalog shows a picture of a traveler with ball bearings, although the parts numbers are not listed.
Thank you everyone for your help on this project. We're getting there.