Sea Cocks, Hose, thruhull's, etc....

[s/v Faith]

Alex,

  I agree.  Experience trumps all the speculation and 'I have read it on the internet that...' in the world.  Those fittings are not gonna wanna come apart, and it is better to remove/glass over them if you have the opportunity.

  I might cap a seacock, but I would not recommend capping the through hull.  If it fit a seacock it would not be properly supported in the hull without the seacock, and if it had been plumed to a ball valve, it is still better to be rid of it.

  The stress imparted to a through hull if hit with even a relatively light object might be enough to break it off.  :o

  I have seen old bronze through hulls where the mushroom has broken off in a grounding (I think it was a grounding, something scraped along the side of the boat underwater....) and the owner said he was lucky to get it up in the hard before it sank.

  ___________________________________________________________

Larry,

  That is really cool of you to offer that...  ;D  Good man.

_{(enjoy the grog)}

[oded kishony]

Lqarry writes:

> Let me know. We could knock it out in a couple of days, and it doesn't have to be consecutive days.<

Larry, you're the best!  :) Thanks for the offer, I may take you up on it.

Oded

[AdriftAtSea]

I have seen old bronze through hulls where the mushroom has broken off in a grounding (I think it was a grounding, something scraped along the side of the boat underwater....) and the owner said he was lucky to get it up in the hard before it sank.

Very likely that bronze throughhull had been weakened by corrosion and de-zincified.  Zinc provides the bulk of the strength in some marine bronzes and without it, there is just a fairly weak copper sponge left behind. 

One key thing to do with bronze seacocks is to scrape the paint off of them and look at the color.  If they have a pinkish tint or hue it is usually a sign of dezincification—and a good indication that they need to be replaced and that your ground bonding of the underwater metal on your boat may need improvement. 

It can also be a sign that the marina or a boat near you  in the marina has a ground fault in the electrical system and that electrolysis is occurring.

[Dougcan]

Hmm bronze does not have any zinc in it, you're thinking about brass?

Basically, brass is an alloy of copper and zinc, bronze is an alloy of copper and tin.

Here's the wikipedia link for brass: http://en.wikipedia.org/wiki/Brass

And the wikipedia link for bronze: http://en.wikipedia.org/wiki/Bronze

[AdriftAtSea]

While my statement about the de-zincification would apply to brass more than bronze,  many alloys of bronze, which are primarily Copper and Tin, do have a slight amount of zinc in them as a deoxyidizer.  Please see this webpage.  While wikipedia is a good reference it often misses on technical materials.   

The other place where zinc is often used is bimini fittings and deck fittings, like cleats, which are often made of Zamac, which is a high zinc content alloy, and should never be used in a marine setting.

[Dougcan]

Interesting, that is something I didn't know before.

I'm not a metallurgist so I'm not qualified to argue this point!   ;D

Still I'm surprised, because I had been told that bronze for marine use contain no zinc whatsoever, but that it's often a high silicone mix.

I do note in the web page you referred to, that zinc is used to insure that the alloy doesn't separate during cooling, but that one can do without zinc by slow cooling or annealing.

It's still interesting though and I thank you for that web link.

[AdriftAtSea]

You're welcome.. .btw, it's a high silicon mix... Pamela Anderson is a High Silicone minx.  :D

[Dougcan]

Excuse me, silicon!  ;D  Darn spell checker! :P

I got curious anyway and went searching for bronze alloys.  I found copper.org (http://www.copper.org), which advocate copper and copper alloys, but also list just about all the alloys and some interesting reference to marine use.

It took me a little while, but I found this http://www.copper.org/resources/properties/microstructure/cu_tin.html which sure enough listed a small amount of zinc in the various common bronze alloys.

But there are also many bronze alloys that contain no zinc, such as aluminum bronzes.

So I guess it depends on just which alloy is used in thru-hull fittings.

An interesting thing I found, apparently, the presence of tin in bronze help to keep the zinc from leaching out.

Now I've learned way more than I wanted to, but it was still an interesting learning experience.

BTW, you did say in your post above that "Zinc provides the bulk of the strength in some marine bronzes and without it, there is just a fairly weak copper sponge left behind."  That's what I was wondering about as tin is supposed to be the "bulk of the strength" in bronzes, otherwise it would be called "brass"?  I'll grand you that there is some zinc, but doubt it's the "bulk" component?

[AdriftAtSea]

BTW, you did say in your post above that "Zinc provides the bulk of the strength in some marine bronzes and without it, there is just a fairly weak copper sponge left behind."  That's what I was wondering about as tin is supposed to be the "bulk of the strength" in bronzes, otherwise it would be called "brass"?  I'll grand you that there is some zinc, but doubt it's the "bulk" component?

True, that statement probably applies more to brass than bronze.  However, removing 2% of the material is probably going to have negative consequences to the strength of the through hull.  The statement is a paraphrase from one of the books on marine maintenance, and if I get a chance, I'll post the exact wording and source. :D

[ronc98]

I am adding seacocks to my c-26 and my current thruhulls are all stainless steel.  Is there any problem coupling stainless steal thruhulls to brass seacocks?  The threads all match up I just want to make sure there is no other compatiblity issues I should be worried about.

[Lynx]

It would be best if you had the same metal. In time they may "weld" together. I do recommend a good anti-seze compound and bond well and keep good zinks.

With this, I do not see much of a problem. In 10 to 20 years you may want to replace the through hulls.

[AdriftAtSea]

Don't do it. You shouldn't be using brass seacocks on a boat.  Brass is extremely vulnerable to galvanic corrosion issues and will de-zincify, leaving behind a very weak copper "sponge".   I wouldn't recommend using bronze with stainless steel for the opposite reason.  IIRC, most marine-grade bronzes will cause galvanic corrosion with stainless steels underwater, and shouldn't be used IMHO. 

Either get stainless steel seacocks, which will probably be fairly difficult to find, since stainless steel isn't a good choice of materials for seacocks, since the lack of oxygenated water will cause the stainless steel to suffer from crevice corrosion--or get Marelon seacocks.  Better yet would be replacing the stainless steel through-hulls with bronze ones and using bronze seacocks on them--since putting a plastic seacock over a metal through hull will eventually lead to the seacock failing IIRC, primarily due to thermal expansion differences.

Finally, don't forget to use a mounting flange with the through hull.  The through hull itself is NPS, and the seacock is threaded for NPT.  Mounting the seacoock directly on the through hull is going to be rather risky, since the seacock won't have the threads from the through hull seat properly. 

Take a look at Rod's site for his article on seacocks and pipe threads.  There's a good photo about two screens down on why you shouldn't mix NPS threaded through-hulls with NPT threaded seacocks.

[Shipscarver]

Well said Adrift!
Your useful and direct response to a frequently asked question is worth listing in a boat care FAQ section.

[ronc98]

Oops I meant bronze seacocks and not brass. 

thanks for all the info and the link.  I already looked over his site and found alot of useful info.  I have all the thread  types matched and the seacocks will be flange mounted. The only part I was not sure of is if could use my Stainless Steal thruhulls or would I need to get bronze ones. 


When I ripped my boat apart I found a time bomb under the head.  The flush water pickup was a plastic fitting with a 3/4 tube fitted over the thruhull.  No clamps and to top it off the hose was a bit loose.  It was just a matter of time before that ended badly.

[AdriftAtSea]

Glad to help Ron... get bronze through-hulls. :)

[CharlieJ]

Marelon saacocks, sitting on fiberglass doublers, through bolted. Bronze through hulls. Had to shorten the through hull to match hull thicknessl

Straight threads on both parts.

Two 1 1/2 inchers mounted, one 1 inch one mounted, one to go when the galley are gets built.

[AdriftAtSea]

Yup.. that's why through hulls are NPS rather than NPT... Couldn't really shorten them if they were NPT now could you?

[CharlieJ]

Sure as the devil couldn't.  :D

But the seacock is also NPS thread- straight all the way to the bottom. I trimmed the through hull so it buries leaving just about 1/16 before it bottoms out. I'd have to go get a flashlight, open the boat, and see what the brand is- can't remember right off. I'll look tomorrow.

Now the BALLCOCKS I've seen some use ARE NPT threaded- they are really intended for shore side plumbing.

[AdriftAtSea]

Charlie-

I'd be interested in knowing what brand it is... If it is Marelon, it is probably a Forespar.  From the Jamestown Distributor website:

Marelon is a formulation of glass-reinforced Dupont Zytel. It is optimized for marine use above and below the waterline with maximum U.V. inhibitors, and it will not support combustion. Additional marine benefits of the material are its extreme range of operating temperature and it's resistance to abrupt changes in temperature.

VALVE MAINTENANCE:

All our valves are non-corrosive, but like any moving part in a marine environment, they required regular inspection and lubrication. Do not fail to actuate the handle and lubricate the seals on a regular schedule (water pump grease or even mineral oil will lubricate seals).

Bottom and top connections are NPS (straight) thread. The use of products with NPS (straight) pipe thread is recommended only for low pressure applications, and then only with a generous application of pipe sealant or PTFE thread tape.

[CharlieJ]

Yep- Just went out to check. Had to check cause I didn't purchase them- owner supplied, but they are Forespar