PS Advisor: 04/15/04
Stuffing Box Hose
I´ve been scouring the Web to try and find what the specs are for stuffing box hose. I know one shouldn't use wire-reinforced hose but I suppose the exact specs are hidden deep in the ABYC rules, which aren't available on the Web. Can you help?
We didn't spot anything specific in the ABYC book about stuffing box hose—the hose that is clamped to the boat's shaft log or stern tube at one end and around the shaft seal (packing gland) fitting at the other. (This is the so-called "flexible" stuffing box configuration found on most modern sailboats. There are also rigid stuffing boxes.) The ABYC does say that "Shaft seals shall be constructed so that, if a failure occurs, no more than two gallons of water per minute can enter the hull with the shaft continuing to operate at low speed."
Having been aboard a boat when the single hose clamp on the shaft log end of the hose failed, and allowed both hose and shaft seal to slide forward a couple of inches, we can say that the thick fan of spray festively decorating the engine compartment for the two or three minutes it took us to fix the problem seemed to us considerably more than four to six gallons. But that's another story.
We did a little hose sleuthing, and when Googling around, came upon Dan Pfeiffer's home page, in which he documents the replacement of the shaft seal on his Pearson 10M. (See http://dan.pfeiffer.net/10m/stuffing_box.htm.) Dan got his hose from Fawcett's, in Annapolis, and showed their part number with the prefix "BUK."
That, we figured, must be a clue. So we called Mike Muessel at Oldport Marine (Our Man in Engines) and asked him where he gets his stuffing box hose. "Buck Algonquin," says he.
So there we have it:
www.buckalgonquin.com.They're a wholesaler, but you can click on the link that says "Shaft Logs and Packing Boxes" to get a rough idea of what they sell. In any case, you can just get the hose at Fawcett's.
We exchanged e-mails with Steve Gaston of Buck Algonquin and learned a bit more.
"Typically, wet exhaust marine hose is used for packing hose," wrote Gaston. "The hose we have manufactured is built on a mandrel. This controls the inside diameter dimension. It is a five-ply construction. Other manufacturers use different numbers of plies. A five-ply construction gives you a rigid and durable hose. The wall thickness can vary, based on how tightly the plies are wrapped.
"Examples of our list prices are:
1-1/2" ID x 12" = $20.30
2" ID x 12" = $27.90
2-1/2" ID x 12" = $39.75
"These are based on 12" lengths. We offer them in different lengths, as most packing box hoses are shorter."
We confirmed that the reinforcing material inside the hose is fiber, not metal, which would eventually rust and degrade the hose.
Both ends of the hose should be double-clamped, with high-quality, all-stainless hoseclamps, and clamps and hose should be checked regularly. Take a screwdriver and loosen the hose clamp screws a turn or two, then retighten, to make sure the screws aren't rusting. (We've all seen "stainless" clamps in which the strap parts are bright and shiny, and the screw parts are just junk.)
The ABYC also says that the whole stuffing box assembly should be located far enough from the transmission coupling that the packing nut can be loosened and slid forward enough for the packing to be changed without removing the prop shaft. That's a very prudent standard.
Shaft removal, unfortunately, is inevitable when it's time to change the hose, so get hose that will last.