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Compass Marine How To | all galleries >> Welcome To >> Re-Packing A Traditional Stuffing Box > GFO, GTU & Ultra-X Warning
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GFO, GTU & Ultra-X Warning

*WARNING: While I do like the graphite impregnated packings such as Duramax Ultra-X, Gore GFO or Western Pacific Tradings GTU they can be dangerous to underwater metals. I have used it on my own boat but inspected the Aqualoy 22 prop shaft yearly.

Graphite is one of the most noble metals on the galvanic scale and is basically at the top. As such anything in the drive train becomes anodic to the packing. Older "bronze" shafts, really more like a brass because they had high zinc content, can be damaged by these new high tech packings.

The damage shown in this photo happened in one season with intact prop shaft zincs. The shaft was in fine condition when packed and a year later this is what it looked like.

The packing used was Gore GFO a graphite impregnated packing. If you have a bronze shaft use extreme caution with graphite impregnated packing materials.

I don't tend to see these issues with Aqualoy 22 shafting but I have seen it with bronze and lower grades of stainless. Please use these packings CAREFULLY. If you choose them please do check on the shaft periodically.

It should be noted that ABYC P-6 specifically says this:

ABYC Standards:
"6.7.4 Graphite impregnated packing material shall not be used because of the possibility of galvanic incompatibility with the shaft material."

That being said there are thousands of happy boaters who have had decent results with these packings. However, they should not be treated as a "set it and forget it" packing. If using these graphite impregnated products I would suggest checking the shaft at least yearly.

Nikon D40
1/60s f/8.0 at 48.0mm iso200 full exif

other sizes: small medium large auto
David 05-Nov-2013 16:06
What is the favored brand and type if one has a bronze stuffing box?
Quickstep 24 with GM1 Yanmar diesel. Thanks much.!