What size packing for my stuffing box?

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Nick F

Guru
Joined
Sep 2, 2020
Messages
598
Location
Canada
Vessel Name
Callisto
Vessel Make
1974 Grand Banks 42 Classic, Hull 433
Hi all,
Can anyone tell me the packing size for my stuffing box? Shaft is 1-1/2". Boat is 1976 CHB34 with Ford Lehman 120.
Thanks for any help.
Nick
 

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I would just measure it. You can back off the adjusting nut and measure it with out much leakage. Drill bits work good.
 
Diameter of stuffing cavity minus diameter of shaft, divided by 2.
Be sure to use a “modern” style packing rather than the “old fashioned” flax.
 
It is probably 3/16"

"Modern" style shaft packing contains graphite. There are documented cases of galvanic corrosion causing shaft corrosion. Read up on it before you decide.

I stayed with flax, Works great and only drips underway. What ever you use check the assembly underway with a temp gauge to make sure it is staying cool.
 
I've read the pros and cons of the graphite in the modern packings. I use the Gore packing and have done now for about 10-12 yrs. I had my shaft pulled for other reasons last month and saw absolutely NO sign of any corrosion.

I ensure I have adequate zincing and I also use a shaft brush.

I have no idea which SS alloy it is so cannot comment on that although I would guess it MAY be 316 or similar. I've had the boat for 35 yrs now and to my knowledge the shaft is original to the boat and is now 43 yrs old.

SO although I won't say the concerns don't not have validity I don't think it is particularly concerning as long as proper zincing is maintained.

I do check the anode voltages every 4 - 6 months so have an idea of what is going on.

As for the packing size I am guessing that it will be either 3/16 or 1/4".
But the advice given so far is good. Use a drill bit set and have those two sizes easily available.
OR use an inside caliper set to approx. size expected. Undo the nut or pressure plate and use the bits/caliper to measure the gap between the shaft and the nut or cavity.

Test the bilge pump first to ensure it is working. You may get a few gallons into the boat but that should be it. Then put the nut back and reset it and go get what you need. I suggest get about twice what you think you will need as you likely will monkey some of it the first time.

I have added my tome about repacking. It should cover most questions but if some come up , then ask.
 

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Our boat had Duramax packing in it when we bought the boat. They don’t drip at all so when I rebuild the stuffing boxes I stayed with Duramax. There was absolutely no sign of any corrosion, just shiny and smooth shafts.
 
I had to repack my rudder shaft recently. I didn't know what size it was, so I just bought a couple feet of every size that seemed likely. I didn't want to get it all taken apart and then realize that I had to run to the store for a different size while water poured into the boat... Total cost, less than $20
 
I had to repack my rudder shaft recently. I didn't know what size it was, so I just bought a couple feet of every size that seemed likely. I didn't want to get it all taken apart and then realize that I had to run to the store for a different size while water poured into the boat... Total cost, less than $20

I had a rudder shaft leak. Thought it was 3/8, had 3/8, 1/2, 3/4 on hand so took it apart only to find 3/8 was too fat. Peeled some of the 3/4 apart and stuffed it in. Worked perfectly well. That was maybe 10 yrs ago, still not leaking.
 
Ha, mine turned out to be 1/4". It was the smallest of the sizes that I had bought :)
 
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