Dripless shaft packing

[edwardc]

While I was on the hard and had the engine out for a rebuild, I repacked the shaft packing with a combination of the graftek packing and the moldable dripless packing. One ring of graftek at the beginning and the end, and the moldable dripless packing in the middle, everything saturated with the synthetic grease that came with the moldable packing.

The instructions say to hand tighten, then start and run, tightening by 1/8 turn at a time until the driping stops. They then caution that the stuffing box will run hotter than a "wet" one, but should be kept under 140 deg.

My problem is that I can't seem to achieve this state. When I first started with it hand tightened, it didn't drip but got too hot. I loosened it and started creeping up on it, but even with the drip rate at 5 seconds, the temp was climbing up to 150 deg with the shaft turning at about 1000 RPM (engine at 2000 RPM, 2:1 v-drive reduction) and the creek water at 68 deg.

A friend at the same marina has a similar setup, and his runs 75 deg with no drips.

I'm at a loss, and I really don't want to have to pull the boat (I just put it in!) and redo the packing.

Any suggestions?

[rpowers]

Packing

Hi Edward,

I have "heard" that the moldable packing stuff is no good (as you are observing).

I recommend this stuff (see photo). I'll running both cool and "dry".

You can change it in the water, just move quickly and use a rag to block water flow for the 15 minutes that it takes.

-Rick

[tartansailboat]

Rick, can you tell me where you purchased this GTU packing? Web site or Worst Marine??

[rpowers]

Jamestown distributors

Jamestown Distributors.

Fairly cheap ($12?).

Good stuff. A square rope of gortex/carbon fiber.


-Rick

[edwardc]

Rick,

The GTU is the stuff I used. The moldable is only for the "interior" rings. You need one ring of some kind of braided packing at each end to hold the moldable in place.

I've heard a number of stories, both good and bad, on the moldable. I did a lot of research. It seems that when you get it right, it works perfectly. My friend has been running it on his Bristol 40 for many years without a single problem.

As for redoing the packing in the water, it will take a LOT longer than 15 min! I have a v-drive. The shaft log sits directly under the engine and transmission, and in-between the engine rails, making access EXTREMELY limited. Tools over 3-4 inches just won't fit. And you can't get "behind" the packing nut to see into it. Even just tightening it is a major deal. See the picture below.

My cutlass bearing is way out on a strut, not in the deadwood. This means that the end of the shaft tube is completely open around the shaft by about 3/8 inch or more. This will admit a LOT of water very quickly when the packing nut is off. One thing I've been considering is going over the side (Brrrr!) and using some modeling clay to seal the open end of the shaft tube to make the water flow manageable. Has anyone tried this?

[CalebD]

Maine Sail

Edward,

If you read the second page on Maine Sail's stuffing box tutorial he describes the problem you can expect with the green clay/dripless packing stuff: http://www.pbase.com/mainecruising/stuffing_box

Modeling clay would probably work to seal up the shaft as would a wax toilet bowl ring.

[edwardc]

Caleb,

Maine Sail's page was one of the resources I used in my research. But I was concerned with some of his conclusions and explainations. For example, he was concerned that the syntef (which came with the moldable dripless packing) had completely sealed any waterflow. But that's the way it's SUPPOSED to work. It really is supposed to be "dripless", not "drip less". It will run hotter than a "Wet" packing, but the packing and the synthetic grease are supposed to hold up to the higher temperatures without breaking down and loosing lubrication.

Another was his claim that "Cavitation bubbles" in reverse could trap air in a shaft that didn't drip. But cavitation "bubbles" are actually vacuum, not air. The prop literally "tears a hole" in the water during cavitation. No air is involved.

I found most of his page to be very helpfull, and the photos to be great.

I'm beginning to wonder if shaft wear is my problem.

[joe_db]

IIRC, cavitation bubbles are steam, not vacuum. Water will boil at ambient temperature at very low pressures. So "sort of" a vacuum

Caleb,

Maine Sail's page was one of the resources I used in my research. But I was concerned with some of his conclusions and explainations. For example, he was concerned that the syntef (which came with the moldable dripless packing) had completely sealed any waterflow. But that's the way it's SUPPOSED to work. It really is supposed to be "dripless", not "drip less". It will run hotter than a "Wet" packing, but the packing and the synthetic grease are supposed to hold up to the higher temperatures without breaking down and loosing lubrication.

Another was his claim that "Cavitation bubbles" in reverse could trap air in a shaft that didn't drip. But cavitation "bubbles" are actually vacuum, not air. The prop literally "tears a hole" in the water during cavitation. No air is involved.

I found most of his page to be very helpfull, and the photos to be great.

I'm beginning to wonder if shaft wear is my problem.

[edwardc]

IIRC, cavitation bubbles are steam, not vacuum. Water will boil at ambient temperature at very low pressures. So "sort of" a vacuum

True, I just didn't want to digress too much into a side topic. The point is, as the bubbles collapse, the pressure goes back up, the water vapor condenses back out, and the bubbles are gone. There's no air involved. I think there's a general misconception that cavitation is caused by sucking air into the propeller, such as you get with an outboard when the prop gets too near to the surface. And when someone gets the physics wrong, and then uses it to try to support their position, I start to get skeptical of their position.

Guess that makes me an old curmudgeon!

But to return to my last question, how much, and what type of, shaft wear is too much? Does it have to be visible "grooving", or is even a wide shallow region of wear bad, even if it's minimal? My PO did not pack the shaft properly, using many pieces of very undersized packing instead of rings of the correct size. I'm beginning to wonder if this didn't harm the shaft. It used to drip like mad when running, almost a steady stream. That was one of my motivations to repack it when the engine was out.

[Dave Neptune]

Fwiw

Edward, I have seen others that have tried to meld the two have the same problem. Go for the straight GTU and be done with it. It still runs warmer but requires no lubrication. The additional warmth could have easily softened the lube enough to let it run out, a common problem with the flax type as well.
Since going to the GTU mine runs a bit warmer and barely drips at all unless running at which it drips about every 20+ seconds or so and that is at 2200 with a direct drive 1" shaft. It's been in for 5 years now and adjusted twice since it set after a few tweaks when new.
The GTU runs a bit wet but barely, and almost not at all when sitting.

Dave Neptune

[marthur]

I am using the green mold-able drip-less packing and have been for approximately 500 engine hours. I remove it to inspect and replace it every couple of seasons. I have not had any problems whatsoever. The shaft log does run warm (but not hot). Warm in this case is 10 to 20 degrees above ambient temp.

Two questions: Did you use enough of the lubricant? (I grease the be-jeebers out of mine). Second, does your friend who is using the mold-able with no problems use flax packing or GTU? I have used flax and teflon impregnated flax with my setup.

[CalebD]

Edward,
I figured you had probably seen Maine Sail's tutorial which, after all is only his opinion.
My opinion is that allowing a few drops of water through when underway helps to both lubricate and control the temperature of the stuffing box.
When I repacked our stuffing box over 5 years ago I used Gore GFO 1/4" packing only and it has worked like a charm with very minimal dripping. (Note to self: check current stuffing box temp underway).
I even bought a kit for the green clay packing and then read MS's opinions on it and I haven't used it yet. I have no personal experience with using this product so I can't offer advice or an opinion on it.
Your engine is in great shape though. Your 'V' drive certainly does locate the stuffing box in a very awkward space. Maybe an overnight or lunchtime 1 hour haul out give you the time to do the deed.

Best of luck.

Caleb,
Maine Sail's page was one of the resources I used in my research. But I was concerned with some of his conclusions and explainations. For example, he was concerned that the syntef (which came with the moldable dripless packing) had completely sealed any waterflow. But that's the way it's SUPPOSED to work. It really is supposed to be "dripless", not "drip less". It will run hotter than a "Wet" packing, but the packing and the synthetic grease are supposed to hold up to the higher temperatures without breaking down and loosing lubrication.

Another was his claim that "Cavitation bubbles" in reverse could trap air in a shaft that didn't drip. But cavitation "bubbles" are actually vacuum, not air. The prop literally "tears a hole" in the water during cavitation. No air is involved.

I found most of his page to be very helpfull, and the photos to be great.

I'm beginning to wonder if shaft wear is my problem.

[ArtJ]

Max wobble on cutlass bearing allowed?

What is the rule of thumb for telling when a one inch shaft needs a new
cutlass bearing? How much wobble when wiggled by hand is allowable
before replacement is required?

Thanks and Regards

Art

[tenders]

>< One thing I've been considering is going over the side (Brrrr!) and using some modeling clay to seal the open end of the shaft tube to make the water flow manageable. Has anyone tried this?

Yes, I've done this myself (actually a diver did it for me) and it does work. I wouldn't leave the boat for any length of time though.

[msmith10]

[QUOTE=tenders;36694]>< One thing I've been considering is going over the side (Brrrr!) and using some modeling clay to seal the open end of the shaft tube to make the water flow manageable. Has anyone tried this?/QUOTE]

How about that foam caulking backer? That was my plan next time I had to repack in the water. I was thinking it could even be stuffed into the inner end of the log around the shaft for the same purpose.