Overheating stuffing box

Twin engine Navigator with Volvo TAMD 63's....tradtional stuffing boxes, flax packed......A week ago, after running for an hour or so at about 1600 rpm's took the temp of each stuffing box with an IR heat gun...Port 85 degrees, cool to the touch....Stbd 150 degrees, too hot to touch.....the shaft into the trans was cool and aft of the stuffing box it was quite cool also..Just around the stuffing box was very hot.....I had my mechanic repack this stuffing box with new flax, set the drip to about 5 per minute with the shaft turning....took the boat out today, 30 mins at 1600 same temp readings....I loosened the nut to about 30 drips per minute and same results after another 20 minutes running......Way to hot with water temp about 70.....Anchored for an hour, box cooled down and ran it again for about 20 mins....Same temp readings, stbd box heated right up.....So-----any suggestions where to look next?? Everything else seems to run smooth and correctly ....

Check the water cooling hose for the stuffing box

sd1209 said:

Twin engine Navigator with Volvo TAMD 63's....tradtional stuffing boxes, flax packed......A week ago, after running for an hour or so at about 1600 rpm's took the temp of each stuffing box with an IR heat gun...Port 85 degrees, cool to the touch....Stbd 150 degrees, too hot to touch.....the shaft into the trans was cool and aft of the stuffing box it was quite cool also..Just around the stuffing box was very hot..

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Perhaps there is a terminology issue here, but how did you get a sense that the shaft, aft of the stuffing box was "quite cool"?

There is no combustion going on in this area of the drive train so the only heat generator is friction. Here are a few possible causes.
- Something is out of alignment or the shaft itself is bent.
- Perhaps there is old packing hiding deep inside the stuffing box that is causing friction.

I'm not sure if 150º F. is too high for a traditional stuffing box or not. Someone with more knowledge on stuffing boxes will likely be around shortly.

I do know that the carrier for the oil lubricated lip seals that seal to my shafts commonly runs as high as 125º F. with no problems.

There was a post recently that pointed to old stuffing that was wedged into the sleeve for the shaft. That may be the cause here, for heat, though it was related to shaft turning by hand restricted.

I don’t remember the exact spec but the stuffing box should be in the 30 to 40 degree hotter range of the seawater, or so. 150 is too hot. Make sure all the old packing is out. Sometimes it is tough to get all of it out.

sd1209 said:

Twin engine Navigator with Volvo TAMD 63's....tradtional stuffing boxes, flax packed......A week ago, after running for an hour or so at about 1600 rpm's took the temp of each stuffing box with an IR heat gun...Port 85 degrees, cool to the touch....Stbd 150 degrees, too hot to touch.....the shaft into the trans was cool and aft of the stuffing box it was quite cool also..Just around the stuffing box was very hot.....I had my mechanic repack this stuffing box with new flax, set the drip to about 5 per minute with the shaft turning....took the boat out today, 30 mins at 1600 same temp readings....I loosened the nut to about 30 drips per minute and same results after another 20 minutes running......Way to hot with water temp about 70.....Anchored for an hour, box cooled down and ran it again for about 20 mins....Same temp readings, stbd box heated right up.....So-----any suggestions where to look next?? Everything else seems to run smooth and correctly ....

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I would respectfully recommend that you ensure the stuffing boxes are well greased not overtight as to cause high temperatures, if they're overtight you'll not only get high temps but also wear on your shaft.
Keep a diligent eye on them until the end of the season.
I would then lift our your boat and fit PSS stern glands, once fitted they are water lubricated and only need an inspection at the start/end of the season to ensure they are working correctly.
I have them fitted for over 15 years without any problems or need for replacement.

If you have a water feed for the stuffing box, I would guess that could be the culprit.

Here are two possibilities. The first one is no water flow, which isn't very likely. Remove the hose at the stuffing box (be prepared to plug the hose barb as it's below the water level), and start the engine to check flow.

The second possibility is an engine raw water issue. This depends on where the raw water take off for the stuffing box is. Some engines have it on the raw water pump. Others have it on the heat exchanger. Let's assume it's on the output side of the heat exchanger. As raw water flow diminishes going through the heat exchanger, the temperature will rise. Flow loss can occur from a fouled strainer, bad impeller, fouled transmission cooler, fouled heat exchanger, or fouled exhaust mixing elbow. I would check where the stuffing box feed off the engine is located and use an infrared temperature gun to measure the temperature of that fitting.

Ted

Over the years we have never been more than 17f above ambient. 2” shaft rotating < 600 rpm. When temps rise it’s always water flow. Sources have varied from the above mentioned to jelly fish clogs air bubbles from crossing wakes causing air to be sucked up into the back side of the cutlass bearing. Check your transmission cooler for stuck zincs as well.

Your stuffing box should be touchable, which I believe is around 140 f. Clearly there is something different from one to the other and as mentioned friction is the only source of heat at the stuffing box. SOMETHING is in there.

Even with old tight stuffing I would think 30 drips a minute (or even 5) should be enough to keep it cool enough to touch it. Prop shafts are expensive. If there isn't a lot more vibration on the hot stuffing box vs the cool one...it is probably time to haul and look at it. Maybe you can hang in the straps over lunch and get the whole thing loose enough to see the shaft where the stuffing box is currently riding.

If there is a lot of vibration on the hot side then address that pretty quick!

Possibly too many rings on the side that is running hot?

sd1209 said:

Twin engine Navigator with Volvo TAMD 63's....tradtional stuffing boxes, flax packed......A week ago, after running for an hour or so at about 1600 rpm's took the temp of each stuffing box with an IR heat gun...Port 85 degrees, cool to the touch....Stbd 150 degrees, too hot to touch.....the shaft into the trans was cool and aft of the stuffing box it was quite cool also..Just around the stuffing box was very hot.....I had my mechanic repack this stuffing box with new flax, set the drip to about 5 per minute with the shaft turning....took the boat out today, 30 mins at 1600 same temp readings....I loosened the nut to about 30 drips per minute and same results after another 20 minutes running......Way to hot with water temp about 70.....Anchored for an hour, box cooled down and ran it again for about 20 mins....Same temp readings, stbd box heated right up.....So-----any suggestions where to look next?? Everything else seems to run smooth and correctly ....

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I have same problem it's seems engine majorly out of alignment shaft rubbing on stuffing box

Another vote for inadequate water flow.

Another vote for too many rings in there. I had to start from scratch learning about traditional stuffing boxes. They're easy to get wrong, even for experienced mechanics. If you have a manual for your specific boat I'd read that. If not, start with 3 rings, 45 degrees offset between each successive ring. I've been able to get it to where there are no drips static and 1 drip in 5 mins underway, 50 degrees above water temp.

I would suggest removing the cooling hose to the box at a convenient location. Ensure there is water flow from outside the boat through the box and hose proving there is no blockage. If this checks OK then I would seal that hose and then start engine and confirm you do have water supply to the box itself. I think this may narrow your diagnosis.

My rule of thumb is stuffing box should be no more than 40F above ambient seawater temp, even without knowing seawater temp you are clearly above that.

Drips per minute are far less important than temp.

You IR gun will not accurately measure the temp of the shaft, it's far too reflective, it often under-reports highly reflective surfaces. Not sure it matters in this case, however.

As others have noted, it does seem like a water supply issue, an obstruction in the log?

The clearance between many stuffing boxes and shafts is surprisingly small, it doesn't take much to inhibit water flow. See the photo in the linked article.

Share some pics, might see something.

More here Conventional Wisdom for Conventional Stuffing Boxes | Steve D'Antonio Marine Consulting

I'm surprised how many people did NOT read the original post!

It is a convention, traditional stuffing box no water line going to it. He loosened the nut till there were 30 drips per minute so clearly there is a lot of water flowing. Even with old rings buried there is plenty of water getting past them - enough to keep the stuffing box cool to the touch.

Actually he doesn’t say no water injection, he says traditional stuffing box. I had a traditional stuffing box that had water injection.

I stand corrected! https://www.passagemaker.com/technical/troubleshooter-understanding-shaft-seals

Still, with 30 drips per minute and still too hot to touch there is more going on than old flax or not enough water getting around.

Since post #2 said check the water cooling hose and there has been no response since then from OP, I am going to assume that solved the issue.

Can you rotate the shaft manually?

OP here.. sorry guys.. Life interfered and was not on this site for the past week.. I do very much appreciate all the responses.. I should have been more clear ref the stuffing box I spoke of.. it's traditional but no water injection... shaft to the transmission is cool to the touch it's just the box itself that is way too hot...in a long talk with a couple of highly recommended mechanics at Shelter Island Boatyard here in town I've decided to pull it out of the water and pull the shaft and see exactly what is going on... will do that in about 4 weeks... I will absolutely post what was found and the remedy..thx again.. all the responses appreciated..

Wings...at the beginning of this I had my diver rotate the shaft...no binding... both shafts rotate easily with the same level of effort...

Have you loosened the nut until water started to drip. And keep going right off if needed, ready to thread back on.

chusansail said:

I have same problem it's seems engine majorly out of alignment shaft rubbing on stuffing box

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I had a similar problem when we bought our 42 fly cruiser from a hire boat company. Rather than fit new flax steam packing and grease it regularly they simply kept tightening it which over time wore grooves in the shaft.
I was lucky I was able to turn the shaft end over end so the grooves were in a different position on the shaft. The engine mounts we're not correct either, one just had a bolt welded to the base plate. The vibration was awful but made a good negotiating point on the purchase price.
To cure the problems we replaced the engine/gearbox mountings for the correct ones. I fitted a flexible coupling between the gearbox flange and the shaft, I fitted a PSS inboard shaftseal and a new cutlass bearing.
I spent maybe 2 hours lining up the engine gearbox shaft coupling as near to perfection as I could get to within 2 thousandths of an inch.
After relaunching the difference was incredible, so sweet and smooth and still is 15 years later. No adjustment need to the PSS seal has ever been needed. When the gearbox guts fell apart (an ex hire boat bodge repair legacy) we replaced it with an identical new Borg Warner 72C and apart from a tiny adjustment at the flexible coupling she's still running sweet.
Not an expensive up date considering all the benefits and above all the peace of mind.
If you have vibration, alignment or stuffing box problems there's only one cure. Start at the engine mounts and work back to the stern tune
If a man made it, a man can fix it.
Perfection is not impossible, it just takes a little dedication.