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Old 26-03-2013, 19:10   #1
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Hot packing gland

Caliber 40 50 HP Yanmar 18" Maxprop 1.25" propshaft

Old Style packing gland with lock nut

Brand new shaft and cutlass bearing
New Teffpack packing (PTFE) - only 2 wraps
Steady drip of water with shaft not turning
absolutely no vibration
engine alignment just completed .003" or less at all points around circumference of coupling

shaft/packing gland interface 60 degrees while sitting at the dock with engine off

all following temps are F at the face of the packing gland where it touches the shaft - measured with a calibrated IR/laser dot remote sensor

5 minutes at 2200 RPM (normal cruise) 105 degrees
5 additional minutes at 2500 RPM (fast cruise) 117 degrees
10 additional minutes at 2500 RPM 135 degrees

I have had the boat for 18 years and have 2800 hours on the engine - I have always used the same calibrated sensor. For the first 17 years and 2700 hours on the engine - I measured ambient water + 25 to 30 degrees under any operating condition at the shaft/gland interface. This was consistent in 42 degree water to 92 degree water

Then, rather suddenly last year, while motoring in the Pacific I noticed the gland/shaft interface was at 140 degrees

I have replaced the packing three times, have removed, cleaned and reinstalled the packing gland, have installed a new shaft, cutlass bearing, motor mounts and realigned the engine/shaft

nothing changes the temperatures - running no drips or steady water flow at the gland results in the same temperature rise

I have always thought that ambient water temp + (up to 40 degrees) was acceptable but I am consistently seeing ambient +55 - 70 degrees

The temperature around the circumference of the shaft/gland interface varies by 10 degrees - it is hottest at the top and coolest at the sides

Any suggestions would be greatly appreciated.

I thought I really understood packing glands / stuffing boxes but I am at a loss as to what to do and am afraid to head off on any long trips here in San Diego since the wind is often none existant
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Old 26-03-2013, 19:32   #2
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Re: Hot packing gland

Switch to using GFO marine packing runs cooler and you set it so no drips. The packing is saturated graphite in a silk soft black braided rope.
I have twin inboard V-8 and never seen them heat up at all.


GFO Packing
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Old 04-04-2013, 21:35   #3
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Re: Hot packing gland - Mystery Solved

It turned out I was turning the packing nut too far onto the stuffing box threads.

When I turned the packing nut 7 threads onto the stuffing box I still could get a steady drip but the packing overheated = ambient + 65 degrees.

When I only turn the packing nut 4 threads onto the stuffing box I get exactly the same water drip but now no overheating - 30 minutes of fast running results in ambient + 18 degrees.

After 30 minutes of fast running the dripping had diminished considerably. The next day I checked and found a drip every 12 seconds and did another 30 minute test - still ambient + 18 degrees.

I waited a few more days and did another 30 minute high speed test and found a drip every 10 seconds and did another 30 minute test - still ambient + 18 degrees.

I guess the packing material was being pushed too hard up against the forward face of the packing gland nut at 7 threads even though it still allowed plenty of water to drip thru.

Packing glands are mysterious things!
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Old 04-04-2013, 21:50   #4
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Re: Hot packing gland

Just saw this thread and my first thought was that you had over-tightened and compressed the packing material
Next time you have to replace, record the number of turns on packing nut and material length.
Replace same but with less turns because of new material and run in at dock with strong spring lines to pilings.
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Old 04-04-2013, 22:10   #5
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Re: Hot packing gland

Quote:
Originally Posted by Pelagic View Post
Just saw this thread and my first thought was that you had over-tightened and compressed the packing material.
+1. Over-tightening is a common error. A hot packing gland needs more flow.
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Old 04-04-2013, 22:15   #6
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Re: Hot packing gland

Also if space allows that you can only install in separate wraps, you make sure the butt ends do not all align in a straight line
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Old 04-04-2013, 22:15   #7
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Re: Hot packing gland

" Over-tightening is a common error. A hot packing gland needs more flow."

That is what is confusing - with the nut turned down only 4 threads there is LESS flow than when tightened down 7 turns yet way less heat.

At 7 threads there was a steady flow - at four turns there was slightly less flow - not steady but individual drops. I actually did the 3 - 4 - 7 - 3 -5 ...etc turns quite a few times to find the location that resulted in the least heat

I suspect when I put the packing in I did not get it placed exactly right and all the too-and-fro of the packing gland (I turned it all the off the stuffing threads several times) finally got the Teffpack/PTFE packing into the correct location inside the gland.
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