GFO and Flax packing sizes are not necessarily the same.
Assuming the shaft size is 1.5", the following lists the sizes to be used and installation practice:
Measure GFO Marine Shaft Packing Size
Its easy to determine which size GFO fiber packing you need. Just measure distance between A and B. (A= I.D. of Suffing Box, B= O.D. of Shaft) Packing size: = ( Diameter A – Diameter B ) / 2
Available sizes - 1/8", 3/16", 1/4", 5/16", 3/8", 1/2", 5/8" - accommodate most power and sail boats. Other sizes available on special order.
Buck Algonquin Bronze Packing Boxes are usually the following sizes and take the following packing size:
Shaft Size Packing Size
1 1/8" 3/16"
1 1/4" 1/4"
1 3/8" 5/16"
1 1/2" 1/4"
1 3/4" 1/2"
• Open the stuffing box
• Remove the old packing completely
• Check the new packing and make sure it's the proper size
• Check the condition of the shaft. Any burrs or sharp areas must be repaired prior to installation
• Wrap GFO fiber packing around the shaft, wherever it's easily accessible, and cut each ring. Or use a mandrel the same size as your shaft to cut rings
• Install GFO fiber packing in the stuffing box one ring at a time making sure that you stagger the joints approximately 90o. It is essential that the ends of the rings meet cleanly at the joint. (Do not add grease or other lubricants - these can hinder performance.)
• Tighten the packing gland until it is snug. Do not overtighten.After about one or two hours of running time, check the stuffing box for leakage, and make a final adjustment to attain minimum leakage. (There should be virtually no leakage.)
The following site has a lot of infomation of boat DIYs. Take a look at "Re-Packing a Traditional Stuffing Box" for information and a warning regarding the use of Gore type packing material.
I apologize for not having a specific recommendation for your issue.