I'm getting about 5 gallons of water a week in my bilge from the stuffing box. I've checked the archives and think a leaky stuffing box is something we can tackle ourselves. We have a Yanmar 27hp 3GM30F engine, but my 1992 engine owners manual doesn't mention the stuffing box. I want to order the GFO dripless packing online. The question is, what size packing (1/4", 3/8", 7/16", etc) do I get without taking the nuts apart to measure and causing a hugh dripping mess upfront? Does anyone have the same engine and have had this done? Thanks for any assist.
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Marcia
Your stuffing box is a separate entity from the engine, so the manual won't mention it. I believe it's boat specific. Are you planning on doing this in the water? If so, you want to get some knowledgable advice. I've always done it on the hard, where pulling the nuts off isn't a leak issue. Make sure you check the condition of the housing & its clamps also. Good luck. PS-Does the previous owner's maintenence log mention it?
Your stuffing box is a separate entity from the engine, so the manual won't mention it. I believe it's boat specific. Are you planning on doing this in the water? If so, you want to get some knowledgable advice. I've always done it on the hard, where pulling the nuts off isn't a leak issue. Make sure you check the condition of the housing & its clamps also. Good luck. PS-Does the previous owner's maintenence log mention it?
"Normally" it is . . . .
shaft size dependent. For my 1979 H37C with one inch shaft I use 1/4" GFO packing. But I am glad I was repowering and the shaft was outside the boat. Two rings of 1/4" is a really tight fit. It would have been really hard to do in the boat. Actually the hard part is getting the old packing out of the "box".
shaft size dependent. For my 1979 H37C with one inch shaft I use 1/4" GFO packing. But I am glad I was repowering and the shaft was outside the boat. Two rings of 1/4" is a really tight fit. It would have been really hard to do in the boat. Actually the hard part is getting the old packing out of the "box".
Avoiding huge messes
You do not want to find out how fast water will come in a loosened, unpacked stuffing box. The force of the water coming in may make it next to impossible to get any packing (regardless of the size) into the unit to stop the water. We had a leak in our rudderstock from a stuffing box that was only just at the waterline and which it appeared the previous owners had never repacked. We were getting about 15 gallons an hour, squirting in like a hose each time we came down off a wave. To slow the leak, we reduced sail and moved the crew forward to get the thing above the waterline. That's not going to be possible with a propshaft. When we went to repack it (and the propshaft) once we were hauled out, we took several different sizes and used the one that fit best.
You do not want to find out how fast water will come in a loosened, unpacked stuffing box. The force of the water coming in may make it next to impossible to get any packing (regardless of the size) into the unit to stop the water. We had a leak in our rudderstock from a stuffing box that was only just at the waterline and which it appeared the previous owners had never repacked. We were getting about 15 gallons an hour, squirting in like a hose each time we came down off a wave. To slow the leak, we reduced sail and moved the crew forward to get the thing above the waterline. That's not going to be possible with a propshaft. When we went to repack it (and the propshaft) once we were hauled out, we took several different sizes and used the one that fit best.
Marcia, before you go to the trouble of...
replacing the stuffing box material, what you have in there may still be okay. Assuming that you have the standard bronze box, break the lock nut and tighten the box housing a flat or two by hand and see if that slows or stops the dripping while the prop shaft is at rest. If so, then you're good for a few more seasons. If not, then... Terry
replacing the stuffing box material, what you have in there may still be okay. Assuming that you have the standard bronze box, break the lock nut and tighten the box housing a flat or two by hand and see if that slows or stops the dripping while the prop shaft is at rest. If so, then you're good for a few more seasons. If not, then... Terry
Leaky box
Marcia, have you attempted to first of all tighten the packing by turning the stuffing boxes 2 large nuts? You will need 2 macho size wrenches. I used large crescent wrenches, they sell special wrenches but I didn't find them especially helpful. As Ed says the packing size is boat specific, and depends on shaft size. I found it EZ to do but it depends on access and the skill level is owner specific. See if you can tighten it first, if that is too difficult you will not be able to handle changing it without help. After you adjust you need to motor a bit and then make sure the stuffing box is not getting hot to the touch. That's why they drip, to stay cool. If it is hot back off the adjustment. If things do not improve easily you'll need to change the packing. Make sure your bilge pump is working correctly before doing anything else. Since my prop shaft is 1 inch and my pushpit tubing is 1 inch I wrapped my GFO packing around the pushpit tubing and cut it to size so it was ready to install as soon as stuffing box was opened and old material removed. My stuffing box actually stopped dripping entirely when I took it apart and did not leak at all as I changed the packing. Mine has a 1 inch shaft and 3/16th" packing. I used GFO. No leaks now, no worries. Good luck, and wear a life preserver. (/kidding)
Marcia, have you attempted to first of all tighten the packing by turning the stuffing boxes 2 large nuts? You will need 2 macho size wrenches. I used large crescent wrenches, they sell special wrenches but I didn't find them especially helpful. As Ed says the packing size is boat specific, and depends on shaft size. I found it EZ to do but it depends on access and the skill level is owner specific. See if you can tighten it first, if that is too difficult you will not be able to handle changing it without help. After you adjust you need to motor a bit and then make sure the stuffing box is not getting hot to the touch. That's why they drip, to stay cool. If it is hot back off the adjustment. If things do not improve easily you'll need to change the packing. Make sure your bilge pump is working correctly before doing anything else. Since my prop shaft is 1 inch and my pushpit tubing is 1 inch I wrapped my GFO packing around the pushpit tubing and cut it to size so it was ready to install as soon as stuffing box was opened and old material removed. My stuffing box actually stopped dripping entirely when I took it apart and did not leak at all as I changed the packing. Mine has a 1 inch shaft and 3/16th" packing. I used GFO. No leaks now, no worries. Good luck, and wear a life preserver. (/kidding)
Repairs at sea
Yet another example of why you want to keep a boat spec book. The PO let you down Marcia. I'd try adjusting the gland (stuffing box) first. Note that if you really have to clamp down on it when you turn it 60 degrees or so you have probably reached the end of the packing strings life and should replace them. A really tight gland will rub your prop shaft the wrong way and result in a worn spot on it. Packing strings are much cheeper and quicker to replace than a new prop shaft. If you want to "go dripless" then that is best done on the hard. If you just want to get through the season so you can go dripless next winter then note that there is a special tool that you can buy that looks like a screwdriver handle with a little hook on the end that makes getting the packing strings out much easier. There are also (usually) 3 packing strings one on top of the other with their ends staggered at 120 degrees. So you can take out the first string to see what size it is without a major leak developing. Also, Something not covered in the books/posts is the need to watch your gland for the first few 10s of engine hours. It will "break in" and you WILL need to readjust it once or twice till it getts settled into its new home. Now go pack some gland! ;-)
Yet another example of why you want to keep a boat spec book. The PO let you down Marcia. I'd try adjusting the gland (stuffing box) first. Note that if you really have to clamp down on it when you turn it 60 degrees or so you have probably reached the end of the packing strings life and should replace them. A really tight gland will rub your prop shaft the wrong way and result in a worn spot on it. Packing strings are much cheeper and quicker to replace than a new prop shaft. If you want to "go dripless" then that is best done on the hard. If you just want to get through the season so you can go dripless next winter then note that there is a special tool that you can buy that looks like a screwdriver handle with a little hook on the end that makes getting the packing strings out much easier. There are also (usually) 3 packing strings one on top of the other with their ends staggered at 120 degrees. So you can take out the first string to see what size it is without a major leak developing. Also, Something not covered in the books/posts is the need to watch your gland for the first few 10s of engine hours. It will "break in" and you WILL need to readjust it once or twice till it getts settled into its new home. Now go pack some gland! ;-)
Thanks for advice
Thanks to all for the great advice. I've relied on this site for great info ever since we bought our boat last Christmas. The PO didn't let us down at all. The boat is 30 years old, in great shape and they are very willing and eager to assist with anything they can (even 6 months later) but most of the time I prefer to just try and figure things out on our own. We are blessed to have such a good old boat, even if she does drip a bit in her old age!! That said, I will heed the advice about tightening the nut (seems too simple to be true!) and I assume it's the larger of the two nuts. If that doesn't work we'll go to plan B (yet to be formulated!).
Thanks to all for the great advice. I've relied on this site for great info ever since we bought our boat last Christmas. The PO didn't let us down at all. The boat is 30 years old, in great shape and they are very willing and eager to assist with anything they can (even 6 months later) but most of the time I prefer to just try and figure things out on our own. We are blessed to have such a good old boat, even if she does drip a bit in her old age!! That said, I will heed the advice about tightening the nut (seems too simple to be true!) and I assume it's the larger of the two nuts. If that doesn't work we'll go to plan B (yet to be formulated!).
Which nut to tighten when...
Marcia, The nuts interact. One nut is a locking nut which acts against the other nut which is used for tightening the packing. I will explain in more detail. Starting from the engine (transmission) and moving towards the stern there are two nuts: The second nut (nearer the stern) is the locking nut which tightens against the first nut (the packing nut which is the closest to the engine). You must loosen the locking nut first in order to adjust the packing nut. You need two wrenches - one holds the packing nut from turning and the other is used to loosen the locking nut After loosening the locking nut adjust the packing nut by turning 1 or 2 flats as previously suggested (you can tell by feel - take up the slack but don't use a lot of strength). I can still turn my 1" prop shaft by hand without a lot of effort after tightening (engine in neutral). Once you have the packing nut where you want it then tighten the locking nut back up ie. turning it to tighten towards the packing nut. (use two wrenches - one to keep the packing nut from turning when you are tightening the locking nut. Check leakage without engine on (there should be none). Then check leakage with engine on and in gear - there should be some leakage - I look for a drop every 10 seconds or so for standard packing. However, the key is enough to keep the packing cool and that depends to some extent on the type of packing - teflon/gore, flax etc. I use flax which is the most readily available and cheapest and works fine. I tend to prefer more leakage than less simply because of the potential damage to the shaft as previously mentioned.
Marcia, The nuts interact. One nut is a locking nut which acts against the other nut which is used for tightening the packing. I will explain in more detail. Starting from the engine (transmission) and moving towards the stern there are two nuts: The second nut (nearer the stern) is the locking nut which tightens against the first nut (the packing nut which is the closest to the engine). You must loosen the locking nut first in order to adjust the packing nut. You need two wrenches - one holds the packing nut from turning and the other is used to loosen the locking nut After loosening the locking nut adjust the packing nut by turning 1 or 2 flats as previously suggested (you can tell by feel - take up the slack but don't use a lot of strength). I can still turn my 1" prop shaft by hand without a lot of effort after tightening (engine in neutral). Once you have the packing nut where you want it then tighten the locking nut back up ie. turning it to tighten towards the packing nut. (use two wrenches - one to keep the packing nut from turning when you are tightening the locking nut. Check leakage without engine on (there should be none). Then check leakage with engine on and in gear - there should be some leakage - I look for a drop every 10 seconds or so for standard packing. However, the key is enough to keep the packing cool and that depends to some extent on the type of packing - teflon/gore, flax etc. I use flax which is the most readily available and cheapest and works fine. I tend to prefer more leakage than less simply because of the potential damage to the shaft as previously mentioned.
Check the right size packing!
I just repacked the stuffing box on my Catalina 30 over the weekend. The boat will go in the water tomorrow. I used the teflon packing West Marine sells. I first bought 1/4 inch but when I got back to the boat and tried to fit it in I realized there was no way I could get 3 pieces of 1/4" in there. I couldn't even get one piece in. I went back and bought the 3/16 which was much easier to fit. If in doubt buy both, they are only about $10 each. The teflon packing comes with grease (sold seperate).
I just repacked the stuffing box on my Catalina 30 over the weekend. The boat will go in the water tomorrow. I used the teflon packing West Marine sells. I first bought 1/4 inch but when I got back to the boat and tried to fit it in I realized there was no way I could get 3 pieces of 1/4" in there. I couldn't even get one piece in. I went back and bought the 3/16 which was much easier to fit. If in doubt buy both, they are only about $10 each. The teflon packing comes with grease (sold seperate).
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