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Old 19-09-2016, 02:34   #16
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Re: bronze fittings in a steel hull

316 SS welded in is the only way to go. If the hull plating is not very thick you may need to put in a doubler. Easiest way to do that is with a slip on flange. Weld the stainless pipe in on both outside and inside and fill any bolt holes in the flange. Trouble free for the life of the hull.
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Old 19-09-2016, 02:59   #17
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Re: bronze fittings in a steel hull

Composite all the way and these ones meet most standards.


Seacocks And Through Hull Fittings | TRUDESIGN

When I first purchased my boat, four of the five SS seacocks were badly corroded. The engine seacock literally fell apart in my hand on the slip.
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Old 19-09-2016, 03:02   #18
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Re: bronze fittings in a steel hull

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Originally Posted by Rustic Charm View Post
Composite all the way and these ones meet most standards.


Seacocks And Through Hull Fittings | TRUDESIGN

When I first purchased my boat, four of the five SS seacocks were badly corroded. The engine seacock literally fell apart in my hand on the slip.
One thought about composite in a steel hull - would there be any chance of damage in a lightning strike?
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Old 19-09-2016, 03:50   #19
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Re: bronze fittings in a steel hull

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"Just weld" stainless steel to common steel is a challenge. I'm sure the pros can do it; at my skill level it takes one pass of the very expensive appropriate wire on the common steel, one pass on the stainless, and then one pass to join them. Then the weld, in this case, must be watertight. This is not a job for an amateur welder like me, nor one I'd like to attempt in a cramped space.
I have found it very easy to weld most grades of stainless to mild with 309 rods using a cheap DC inverter stick welder.

But I second RC's Truedesign option. The only real issue is fire. Lighting isnt an issue. I have just installed a very expensive forespar Marelon seacock in my alloy hull, but I wish I had known about the Truedesign ones before I bought the forespar one. They look much better.
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Old 19-09-2016, 03:53   #20
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Re: bronze fittings in a steel hull

welding a 316 ss through hull to a mild steel hull is easy peasy..... as long as you use some 309 rod.... don't use 304 or 316 rod or you will have issues later. Simple stuff... btw why do have a steel boat if you can't weld?? practice...take a welding class ... It's pretty enjoyable stuff and a skill you need to aquire if you have a steel vessel.
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Old 19-09-2016, 03:56   #21
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Re: bronze fittings in a steel hull

With truedesign, the loadbearing collars http://www.trudesignplastics.com/mar...earing-collars make them much stronger for approval as a proper seacock, rather than just a normal ball valve.

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Old 19-09-2016, 08:57   #22
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Re: bronze fittings in a steel hull

Marelon is a very good product but not as fireproof as stainless steel. 316 stainless ball valves are less expensive, very strongand widely available. Remarkably 316 stainless is not too far from steel in the galvanic series of metals so electrolisis is limited and easily managed with sacrificial anodes or other active means. The epoxy barrier coating, sealing the flooded interface between different metal is the primary method of protecton. No electrolyte, no battery, no corrosion.
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Old 19-09-2016, 09:14   #23
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Re: bronze fittings in a steel hull

Welding ss to steel is not a problem. Use 309 ss welding material. On the other hand galvanic corrosion loves weld joints so, if possible, I would stay away from creating welded joints between different metals below the waterline.just buy a $1 nipple at home depot, cut it in half and you have two good hull pipes, thread and all. Weld them directly to the shell plate or better into the seachest wall.
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Old 19-09-2016, 09:30   #24
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Re: bronze fittings in a steel hull

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316 SS welded in is the only way to go. If the hull plating is not very thick you may need to put in a doubler. Easiest way to do that is with a slip on flange. Weld the stainless pipe in on both outside and inside and fill any bolt holes in the flange. Trouble free for the life of the hull.
Hum, would be concerned about stainless given its love of crevice corrosion, brittleness, and tendency to go bad in an anaerobic environment. Would also have some questions if it was subject to heated water on a continual basis. And as someone else mentioned, the welds really suck. Had a stainless lifter that failed in three years due to welds going bad, and the welds were done by a professional welder.
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Old 19-09-2016, 17:45   #25
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Re: bronze fittings in a steel hull

No worries about a 316 nipple welded to mild steel with 309. The welds do not suck and are easily done if you know how. I'm not sure where you guys are getting your info but you obviously have been led down the wrong path. If you have had weld go bad in a 'lifter'... and I think you are referring to a riser,,, then it was probably done with the wrong material or rod. if you build it out of 304 then you will have a problem. if you use 304 0r 308 rod then again you will have a problem. If you use 316 rod or 304 ,308 and weld stainless steel to mild steel and subject it to salt water you will have a problem. If you are using 304 for your base material you will have a problem...especially when you run hot salt water through it.These are all dissimilar metal troubles that can be worked out by using the right material for the right job.
Same thing for black water tanks....304 stainless and urine don't agree with each other.
Unless the "professional welder" is thoroughly knowledgeable with marine welding and materials he will use the wrong thing and you will get undesirable results. They will look "pretty" at first but later after use they will experience electron transfer --(simplistically one alloy is robbing material from the other)-- and you will see corrosion, cracking,pinholes ,etc.
You will see this when welding ss stanchions to decks,,hardware,, hauser rings etc.
Basically just because its stainless doesnt mean it is fit for the marine environment....it should be 316 alloy and above.
I wouldn't be a fan of using plastic through hulls on my steel boat. You bought the boat for the strength of the hull,,, why compromise its integrity with a marelon through hull that can shear off in a crunch. Just seems silly ....
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Old 20-09-2016, 16:33   #26
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Re: bronze fittings in a steel hull

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Any scrap yard around here has barrels of SS nipples and SS ball valves at $1 a pound .just weld in a threaded nipple or stand pipe. Suitable backing plate may be needed to beef up the hull skin
sounds like the coast guard would love that!
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Old 20-09-2016, 16:52   #27
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Re: bronze fittings in a steel hull

Like a lot of people have said, use a 316L nipple for the thru hull. It is important that the nipple be rated 316L, not just 316. The "L" rating means low carbon and welds on L rated 316 are quite corrosion resistant. Plain 316 welds are much more corrosion prone.

Use 309L rod. This is easy to weld, proven long term reliable on scores of boats. Use 316 ball valves, much cheaper than marine seacocks and extremely reliable long term.
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Old 20-09-2016, 17:19   #28
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Re: bronze fittings in a steel hull

Don't know if the cg loving comment was based the (horror)hint of recycle or what. Perhaps I should have mentioned that Paper mills and breweries all use the best 316 SS and scrap most stuff when modifiying or upgrading . I visit with a zip blade cut off grinder in my pocket so I don't buy more than I need if it comes in big pieces Sourcing the best stuff available or buying a plastic valve... a no brainer. Many steel boats are so flimsy plated that some reinforcing is necessary I just assumed that if you are welding, you would have learned how before you decide it can't be done right.
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Old 20-09-2016, 17:25   #29
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Re: bronze fittings in a steel hull

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Originally Posted by s/v michaela View Post
welding a 316 ss through hull to a mild steel hull is easy peasy..... as long as you use some 309 rod.... don't use 304 or 316 rod or you will have issues later. Simple stuff... btw why do have a steel boat if you can't weld?? practice...take a welding class ... It's pretty enjoyable stuff and a skill you need to aquire if you have a steel vessel.
309 or 308 filler for 316 to steel. The key is to avoid too much carbide precipitation in the heat effected zone.

If you're a competent welder it's a common dissimilar metal weld. Otherwise use a marelon thru hull.

Others have proposed more complicated but best practice options.

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Old 21-09-2016, 00:09   #30
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Re: bronze fittings in a steel hull

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Hum, would be concerned about stainless given its love of crevice corrosion, brittleness, and tendency to go bad in an anaerobic environment. Would also have some questions if it was subject to heated water on a continual basis. And as someone else mentioned, the welds really suck. Had a stainless lifter that failed in three years due to welds going bad, and the welds were done by a professional welder.
The thing is that even a very badly done welding job is likely to produce a stronger more reliable hull fitting than any of the alternatives, particularly plastic (generic term for non metal polymer type products) Entirely different matter with rigging fittings which are subjected to high levels of cyclic loading.

I have a mixture of SS and carbon steel thru hulls on my 29 years old steel boat and have never had any problems with any of them.
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