Stuffing Box Seal Replacement

[buoyohbuoy]

Hi,
We have only 256 hours on our R25SC but had to have the stuffing box packing replaced. It turned into a bigger job when the packing nut was so seized that the transmission had to be removed to make the repair. The packing had already been adjusted a couple of times last year and there was no more adjustment room left on it. My question is: is this unusual for a boat with so few hours on it? I'm concerned that there might be some kind of shaft misalignment that might be contributing to premature seal failure. Any thoughts would be appreciated.

Cheers,
Mike
2014 R25SC "Daria"

 

[Favunclerich]

Mike,

Yes, replacing the stuffing box packing at 256 hours is very unusual. I replaced the packing on Roam at around 1500 hours. It could have gone longer, but I was adjusting the nut every 30-40 hours, so I figured that it was time. How often were you adjusting the nut, and what was the drip rate before and after each adjustment?

It's certainly possible that misalignment or scoring to the prop shaft are the root cause of your problem. I suppose that there could also be a defect with the stuffing box itself or the original packing.

I suggest watching how things develop over the next 100 hours or so.

Rich

 

[knotflying]

Something does not seem right here. I would assume that if you made adjustments in the past year the nut would not be frozen on the threads. When making adjustments they should be very very slight. Like turning 1/8 inch at a time. You should get 1 drip about every 20 seconds and practically none when the shaft is not in motion. Using an infrared thermometer the nut housing should be no more than 10 to 20 degrees higher than the water temperature that your boat is in. I am also trying to figure out how removing the transmission enabled the removal of the nut. The nut screws to the stuffing box and slides over the shaft. It has nothing to do with the transmission. One could uncouple the shaft from the transmission and remove the collar that bolts to the shaft and then slide the entire shaft out and the nut will still be on the stuffing box. I make it a practice to spray some PB blaster on the stuffing box nuts and keep them free.
As Rich suggested, you may want to check your shaft alignment to make sure that is within tolerance. I would also, while in the water, remove the hose that goes to the stuffing box and make sure water flows out of the fitting. Plug that fitting with a pencil our wood plug and then turn on your engine and make sure water is running from the exhaust elbow through the hose. The reason I suggest this is that I have seen the fitting at the elbow get clogged and no water coming out. You just want to make sure that you are getting enough water flow to keep things cool. Overheating the packing will definitely cause premature failure. I think, but not 100% sure, that your exhaust elbow is supposed to be inspected at 250 hours, but it may be 500 so check the manual. Removing it and cleaning it out is not a difficult job.

 

[Two killicks]

Here is what I have read about the two most common reasons for this situation to happen (taken from the website Cruising World)

The first and most common cause of chronically leaky stuffing boxes involves the condition of the surface of the propeller shaft directly beneath the packing. If it's in any way irregular, pitted, or damaged, the packing will be torn up each time the shaft rotates beneath it, which may be as many as 1,500 or 2,000 times per minute. The pitting or damage is often caused by the stuffing box's oxygen-poor environment. If this is the case, then no amount of repacking-regardless of the type of space-age "leak-proof" material you use-or adjustment will resolve the problem. Two solutions exist: Replace the shaft, or use a longer or shorter stuffing-box hose to move the location of the packing over an undamaged section of shaft.

The second problem, which also results in chronic leakiness, is often caused by a sailor's response to the first problem: overtightening the nut that contains the flax packing. When the nut is overtightened, the flax overheats, and the wax lubricant melts and runs out. Green or black sticky material under the box means that the stuffing box has overheated; the box must now be disassembled. Clean out all vestiges of packing and wax, then clean the shaft and lightly polish it using 400-grit emery cloth.

It might be wise to check the shaft to see if there is pitting on in before replacing the stuffing box...

Hopefully this article will help you to troubleshoot this issue.

Please let us know about the outcome of your problem.

 

[Irish Mist]

Could someone tell me wrench size for R29 ? I thought the rate of dripping was while stopped, I need to tighten mine for sure. I am getting a drip about ever 5 seconds while stopped, which from my reading I see now is too much for underway and way too much at the dock.
Thank you

 

[knotflying]

On the 27 it is 2-5/16. You can buy one of these adjustable wrenches that are also in most hardware stores (known as a slip nut wrench) and are less costly. http://www.westmarine.com/buy/seafit--adjustable-packing-nut-wrench--290280. You need two wrenches. One to hold the lock nut and one to hold the packing nut. These wrenches are not the greatest, especially if you need to loosen a seized nut. As I said a spray of PB Blaster and let it sit overnight.
Do not just tighten until the water stops while at the dock and not in gear. I suggest that before you leave the dock free up the nuts and then tighten in place. Then run around a little and get things warmed up. As you are running, tighten very little (1/8 inch movement of the nut) and then time the drip. At about 20 seconds between drips you are done. Tighten the back nut up to the stuffing nut and lock in place.

 

[Gin]

Knotflying, 20 seconds between drips in gear, running? I assume no real throttle, though? And no drips out of gear running at the dock? I've never been clear on any of this . . .

Gini

 

[Irish Mist]

Thanks, I will try to purchase the proper wrenches to keep with the boat, I will go at this cautiously as I would rather more drips the. Too tight

 

[knotflying]

Knotflying, 20 seconds between drips in gear, running? I assume no real throttle, though? And no drips out of gear running at the dock? I've never been clear on any of this . . .

Gini

The shaft shaft needs to be turning, so you could either go out with someone who can pilot the boat and you open the engine compartment and watch for the first drip, then start timing the subsequent drips. If too much water is coming out, then it may not drip but rather sling water around. This may be indicated by a darkened line that has developed on the port side of the bilge in line with the stuffing box nut.
With the back nut loosened tighten the stuffing nut a bit and keep running in gear.

If you are at the dock, then tie the boat up well and put it in gear at slow speed and do the same observation and tightening.

Again, tighten at small increments, waiting and then timing after each move, until the drip slows to about 20 seconds.

Trying to tighten the stuffing while the shaft is not turning may result in over tightening. When it comes to the stuffing it is better that it drip a bit more often then not as often so that it won't overheat. You may still get a slight drip when stationary, but it should be very long periods between each drip. Most often none at all.

 

[Gin]

Knotflying, thank you! That is a very helpful step-through. I won't be checking mine until closer to spring, but when I do, that will be a big help. In your debt.

Gini

 

[sheral]

Lots of help here from some very knowledgeable people. Thank you!

 

[Irish Mist]

Lots of help here from some very knowledgeable people. Thank you!

So true