Whats the difference in construction between packing shaft hose and exhaust hose? Has anyone torn both apart to analyze the internal construction?
Packing hose vs exhaust hose
- Thread starter Project_Mayhem
- Start date
Shaft log hose is much thicker than exhaust hose and has multiple layers of reinforcement. It’s so thick and sturdy that it actually takes several days to completely tighten the hose clamps.
I think the reason for this may be that shaft log hose is subjected to engine vibration, lateral movement in relation to the hose, at one end and no movement at the shaft log end which is less than a foot away. This kind of differential movement puts sheer stresses on a short length of hose that will quickly cause thinner exhaust hose to delaminate and fail. It’s also a hose that is more difficult to change, requiring that either the engine or the shaft be pulled. It’s not a quick, easy fix if it fails.
It’s tempting to substitute cheaper exhaust hose, and many do, but it’s not the right use of that kind of hose. Shaft log hose is designed for this purpose.
I think the reason for this may be that shaft log hose is subjected to engine vibration, lateral movement in relation to the hose, at one end and no movement at the shaft log end which is less than a foot away. This kind of differential movement puts sheer stresses on a short length of hose that will quickly cause thinner exhaust hose to delaminate and fail. It’s also a hose that is more difficult to change, requiring that either the engine or the shaft be pulled. It’s not a quick, easy fix if it fails.
It’s tempting to substitute cheaper exhaust hose, and many do, but it’s not the right use of that kind of hose. Shaft log hose is designed for this purpose.
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Shaft log hose is designed to resist the constant torquing that occurs on the packing gland. Unlike other hoses and fittings that go below the waterline you can't shove a bung into it if starts to fail. A failing shaft log hose is a catastrophic failure, you best hope someone is nearby to pluck you out of the water.
Thanks. Torquing is a better description than lateral movement. Sheer is the result of both.
I'm also seeing heavy duty shaft log hose. Is this really necessary on a 23hp motor? On a 150+ it makes sense but I'm skeptical for a sailboat. Surely doesnt hurt
Overtighten your packing on an engine with a vibration problem and then see how you feel about it
!
Because the prop shaft passes through it. Have to pull either the engine or the shaft, or at least uncouple the shaft and slide it down if you have the space, in order to replace the hose, regardless of hose type.
Yes, regardless of type. That's what had me confused with your comment. I thought you were suggesting that replacing real stuffing box hose was somehow different in that respect.
Got it. Only difference with actual shaft log hose is what I mentioned about it taking a couple days to completely tighten down the hose clamps because the hose is so thick.
Buck Algonquin makes a log hose but it doesn't say heavy duty. It's surprisingly difficult to find in 1-5/8".
CD's regular hose. I think they're trying to pass off exhaust hose as log hose.
Stuffing Box Hose Kitw/ Clamps 1-5/8" I.D.
CD's heavy duty hose
Stuffing Box HD Hose Kitw/ Clamps 1-5/8" I.D.
I'm looking at BA as well as Catalina Direct's heavy duty kit. Price for one installation ends up being the same even though you'll get 12" with BA
I got me a brand new coupler, shaft and cutlass! We suspect the yard lifted the boat by the shaft prior to me buying it. There was visible wobbleOvertighten your packing on an engine with a vibration problem and then see how you feel about it
Right. I’ve changed it out before. Really thick stuff. I need to do it on my current boat as well.
I’ld be curious who manufactures the hose that CD is selling. I’m sure it’s good quality. If they‘re selling it in the length you need and including good quality hose clamps, it looks like a good deal. I don’t recall what I paid for BA hose and four solid ABA hose clamps, but I‘ld bet it was more. I had to buy a 12” length of BA hose and cut it down to five or six inches with my utility knife. I may not recall the price, but I do remember blisters on my hand from cutting that thick hose. A utility knife may not have been the best tool choice. If you can get it precut to the length you need, it will save you some time and toil.
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I always swear by a brand new 32 TPI hack saw blade for getting through sewage and exhaust hoses.
Haven't had the pleasure of cutting a log hose yet and from what I've seen here, not looking forward to it either.
@Project_Mayhem,
Dave,
Ou are putting a lot of money into your new boat and upgrading things as you go…this might be a good time to consider switching to a dripless seal of some sort.
i like the Volvo Penta dripless rubber seal, for its low cost and simplicity. But as we discussed, I do “burp” it every time I open the engine intake because it is right there in the engine bilge. If that is not convenient on your boat, you could consider a design that has an air line on it for purging air out of the seal. The PYI version allows for that.
Greg
Dave,
Ou are putting a lot of money into your new boat and upgrading things as you go…this might be a good time to consider switching to a dripless seal of some sort.
i like the Volvo Penta dripless rubber seal, for its low cost and simplicity. But as we discussed, I do “burp” it every time I open the engine intake because it is right there in the engine bilge. If that is not convenient on your boat, you could consider a design that has an air line on it for purging air out of the seal. The PYI version allows for that.
Greg