Removing old/corroded seacocks - SailNet Community
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post #1 of 17 Old 10-22-2010 Thread Starter
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Lightbulb Removing old/corroded seacocks

I had trouble finding an article instructing how to do this, so I wrote about how I did it and would like to share:

One of the things I knew about Windsong when I first saw her was that all of the seacocks needed to be replaced ASAP. They are very old-school style Groco seacocks and all have corroded to the point where they are inoperable. What does that mean? If a hose were to leak, I would not have had a way to shut off the thru-hull and the boat would probably sink unless the hose or seacock was plugged.

Seacocks are meant to be the #1 insurance on the boat against sinking, and I didn't have that insurance for the entire time I owned the boat in the water. Since I started the bottom job I have been contemplating how the heck to get the seacocks and thru-hulls off the boat. They were so corroded that unscrewing the thru-hull from the seacock was impossible. I spent many months contemplating my approach and did as much research I could on the subject. Unfortunately there aren't many articles written on how to get this job done on old, corroded equipment. There are plenty of articles on how to take apart modern seacocks, but non on how to tear apart old ones with no hope of reuse.

I did, however, find a few blogs and forum posts from people who just cut the thru-hulls up with a Dremel or some other tool to help remove them. But with my limited experience in doing things like this, I really needed a step by step instruction on how the heck to do that. After some creative thinking and experimentation, I finally figured out how to do it and here I will show my process.

Here are the seacocks in the head with hoses removed. One is the sink drain, another is for the head itself, the other was unused with no plumbing coming from it.



Here are the thru-hulls attached to these seacocks



Each seacock has two bolts that go through the hull that needed to be removed. My dad and I began this job back in May by removing the hoses to the seacocks and the bolts that go through the hull. Once we reached that point, we were stumped as to how to remove the thru-hull from the seacock. So after my research I took a stab at cutting the thru-hulls to remove the mushroom head so I could just pull the seacocks out from the inside.

I removed the three thru-hulls from the head seacocks before I got down there with the camera, so the sequence below shows the thru-hull from the galley sink. As you can see, the two bolts are still attached so I wasn't able to actually remove that seacock until I get a second hand, but the process is still shown.

First, using a cut-off wheel on my Dremel tool, I made a series of cuts to create some pie wedges. For the bigger thru-hull in the head, I needed to make a few more slices.



In my research I learned that bronze is a pretty soft metal, so cutting and bending is quite easy. In this next step, I hammered a scraper/chisel under one of the slices and pulled down to bend the slice outwards a little bit, enough to fit the back of a hammer under the slice.



With the hammer under it, pry the piece right off. The pieces pried off surprisingly easy.





Repeat the process for each slice until all you have left is a the clean shaft of the thru-hull in the hole.





At this point I went inside and removed the seacock by just pulling it out. One seacock just fell off after cutting the mushroom, one needed to be pried off with the back of the hammer, and the other just needed some muscle to pull out. Here is the head area with all removed:

Outside:




Inside (thats a flashlight in the middle):



Old seacocks. You can see how corroded they are, no hope for the valves to turn. They are not the newer style Groco seacock with a locking nut on the base.





After figuring out this process, removing these things is a piece of cake. I'll need some help to get the remaining seacocks unbolted, but I am no longer worrying about the process when comes time to start fairing and repairing the bottom.

I'll be using these articles as reference to install new thru-hulls and seacocks (links):

Seacock and Thru-Hull Primer
Replacing Thru-Hulls and Seacocks
Seacock Backing Plates

My boat rebuild/sailing blog:
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post #2 of 17 Old 10-22-2010
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You did a good job. I also use a Dremel for many things on the boat. But an angle grinder would have made fast work of that job.

The links you are using to replace them (by Maine Sail) are excellent.

Brian
Living aboard in Victoria Harbour
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post #3 of 17 Old 02-01-2011
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I had the same issue on my downeaster, same seackocks. I used an angle grinder and ground the heads right off. It took me about 5 minutes per.
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post #4 of 17 Old 02-12-2011
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Excellent post, thanks for the detailed info and photos.
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post #5 of 17 Old 02-12-2011
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Angle grinders make quick work of through hull + seacock removal, BUT, you can easily overheat the surrounding FRG.
So, for 'recalcitrant' grinding (especially for TRUE bronze that has the absolute minimum of zinc component, zinc added for ease of 'machining'. Without zinc, bronze is a 'b!tch' even to 'grind') the hacksaw method combined with or in combination of the angle grinder method is a good way to remove and not 'overheat' the FRG.

The better and more expensive alloys of bronze have very little zinc, and a very hard to grind, cut, or machine. NiAl-Bronze is probably the 'hardest'; most of what you find on rec. boats is really a 'Red Brass' because its loaded with zinc to make it cheaper to machine, and is therefore easier to cut or grind - but you better have sufficient zinc anodes elsewhere because if you dont the zinc within the Red Brass (faux bronze) will become the 'anode'.
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post #6 of 17 Old 02-12-2011
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Quote:
Originally Posted by RichH View Post

The better and more expensive alloys of bronze have very little zinc, and a very hard to grind, cut, or machine. NiAl-Bronze is probably the 'hardest'; most of what you find on rec. boats is really a 'Red Brass' because its loaded with zinc to make it cheaper to machine, and is therefore easier to cut or grind - but you better have sufficient zinc anodes elsewhere because if you dont the zinc within the Red Brass (faux bronze) will become the 'anode'.
Most good quality UL Marine rated seacocks are made from 85 three 5 bronze which has very little zinc. Apollo, Groco, Spartan and many others use 85-5-5-5 bronze which is supposed to have less than 5% zinc.

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post #7 of 17 Old 02-12-2011
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TRUE bronze has nil or trace % zinc ... and is an absolute ROYAL and expensive PITA to machine.
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post #8 of 17 Old 02-12-2011
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Originally Posted by RichH View Post
TRUE bronze has nil or trace % zinc ... and is an absolute ROYAL and expensive PITA to machine.
I don't know of anyone in the marine industry that ever used true bronze with no lead or zinc for machining. Seeing as bronze is a copper alloy I don't even know what a true bronze would be? Perhaps just tin & copper? Considering that nearly every maker of seacocks from Spartan to Apolo, Groco & Buck Algonquin has used 85 three 5 bronze and it is about the most resistant to dezincification we see in the marine world I would have to consider that a good marine bronze. Prop & shafting bronze has a LOT of zinc unless a NiBrAl prop...

As you said very tough stuff even at 85 three 5. I have seen 40 year old bronze seacocks clean up and look like new with no signs of pitting or dezincification and continue on. Well made bronze seacocks will last a long, long time. You can still buy Spartan's but they are getting expensive.

I cringed at the OP discarding those beautiful old seacoks because I have restored ones that looked just like that to near new condition provided there was no dezincification. It is rare that I have seen deszincification on a true 85 three 5 bronze. Verdigris yes, dezincification very rarely...

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Last edited by Maine Sail; 01-04-2012 at 09:37 PM.
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post #9 of 17 Old 02-13-2011 Thread Starter
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Originally Posted by Maine Sail View Post

I cringed at the OP discarding those beautiful old seacoks because I have restored ones that looked just like that to near new condition provided there was no dezincification. It is rare that I have seen deszincification on a true 85 three 5 bronze. Verdigris yes, dezincification very rarely...

I'm still holding onto them. I figure I could get something for them, or restore them myself some day. I will be buying new ones for my boat though.

My boat rebuild/sailing blog:
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post #10 of 17 Old 02-13-2011
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Excellent job and a very creative solution. I'm not sure what I would have done in you shoes, but now I have a great idea filed in my cluttered memory. Good work!

One suggestion for the future is that when using the hammer, use a piece of 1/2" plywood as a backer. This will prevent distortion of the underlying material. In this case, it didn't matter because the hull was clearly thick enough. But if you were removing something on a nice wood like teak ply, you could end up with indentations or crushed material.

Just a habit that I've formed after buggering too many surfaces (wallboard, fine wood, etc.)

Sabre 38 "Victoria"
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