Keep, Fix or Junk these Seacocks?

[raahell]

Hi everyone,

I've taken an inventory of the nine seacocks on my steel hulled sailboat. I'm posting pics of the ones I'm concerned about. Take a look-see and let me know which ones you would KEEP, MODIFY or JUNK. And let me know why. I'm especially interested to hear from people experienced with metal hulls.

Here's a few questions to ponder over while you're looking at the seacocks:

1. The first two pics shows one of 3 seacocks that have a stainless steel thru-hull comprising a base and welded-on nipple on inside and a stainless steel plate on outside, with 4 bolts holding the assembly together to the hull plating. Does anyone recognize these as a manufactured thru-hull (I can't find any markings)? Might these be home-made? They appear to be in very good condition and are quite sturdy.
2. The rest of my thru-hulls are mild steel pipes welded directly to the hull plating. I've already found a couple that are heavily corroded and have cut them away with the intention to install Marelon wide body composite seacocks. Do you recommend replacing all of the welded on thru-hulls?
3. Several of the seacocks comprise a combination of stainless steel (some stamped "316L", some with no stampings), mild steel and/or galvanized fittings. What combinations - if any - would you tolerate to have attached to your metal hull?

Looking forward to hearing from wiser folks than me!

[EngNate]

Yes, home made. Obviously they've been tough enough, and will be if still in fine condition (be sure to check inside for pitting). But they are not as strong as a cast SS thru-hull fitting, and the thru bolts are a likely weepage point. With the caution noted below, re using these isn't going to compromise your boating or ownership experience, IMO.

! One thing that's very important here is that SS and bronze materials must be electrically isolated from the hull or you will have corrosion around and under the fittings. Washers and bushings of something like Delrin plastic need to be used, I just have a hunch you're not going to find them installed. Composite seacocks are a good option to avoid corrosion and protection issues, but they are not as strong as metal, and must be secured with their 4 bolt holes and those isolated from the hull. Use only 316 hardware here.

Mixing plain steel and galvanized is fine. Any SS or alloys of copper will corrode the steel/galvanized/black iron that it is in contact with. This is always a thing with metal boats. The commercial solution is use steel and replace it when needed. I hear the tale from time to time, pushed on the handle and the whole thing broke off. Protection from anodes on the hull does not extend far at all into a passage so these unions are un protected. These interactions won't extend out to affect your hull plating in most cases, but you want no dis similar metal underwater in contact with your hull.

My recommendation for best is 316SS threaded thru hulls with appropriate isolating hardware and 316 valves.

The welded in nipples, if they're old enough to have a thick layer of scale inside they ought to be replaced. If not, de-scale and examine the passages inboard ends for pitting.

[raahell]

Thanks EngNate.

I don't see any isolating material between the home-made thru-hulls and the steel plating. I've heard that some installers will create isolation with the caulking by only partially tightening the fitting at install, then tightening it further after the caulking has cured. What do you think of that technique?

Anyway, I will remove the home-made seacocks to check for internal pitting, before making the decision to KEEP, MODIFY or JUNK. Great point and thanks for that!

Back to galvanic isolation: I've got some High Density Polyethylene (HDPE) sheet (1/8" thick) which I've been cutting to shape and using to isolate my deck fittings from the deck plating. Do you know if HDPE is suitable to do the same under the waterline? I know that High Modulus High Density Polyethylene (HMHDPE) is suitable for underwater use and is used to make rudder bearings and such, but that material is much harder to source.

Also, I think I'm correct in saying that for the isolation to be acheived, non-conducive washers have to be used on BOTH sides of the hull. No? As an example, I have a recently purchased all-bronze mushroom-type thru-hull that came with a B&G transducer. It came with only one rubber washer, however, which the instructions say to use on the inside. I just don't understand how that will isolate the bronze from the steel when the bronze remains in contact with the external side of the hull plating. What should I do here?

Finally, even if I make some washers for both sides of my home-made SS thru-hulls, I've still got the issue of the sides of the bolt holes being in close enough contact with the thru-bolts that conduction will nevertheless occur. So should I make the holes larger and then add nylon sleeves?

It seems to me (and I'm ready to be convinced otherwise) if I were to take the galvanic isolation issue REALLY seriously (which I agree IS IMPORTANT), a decision to use any metal fitting on a metal boat incurs a number of extra steps to really, properly isolate them from the hull. These additional washers, sleeves, larger holes, etc, will likely not be as per the mfr instructions and therefore may compromise their integrity in some way or another. For this reason, the alternative of using properly designed and ABYC approved composite fittings, which can be installed simply and exactly as per instructions, is more attractive at this point.

BTW, the composite seacocks I'm considering are mushroom type, have very wide bases and have no thu-bolts. See https://www.defender.com/product.jsp?id=6148983 . These have been tested and far exceed the ABYC standard (500 lb sideways force for 30 sec) testing. There's some excellent videos on YouTube showing the test. For some weird reason many marine suppliers don't carry this more robust line of Marelon fittings, only the ones with triangular bases which many people (and even some manufacturers) install incorrectly.

I look forward to more responses.

[tkeithlu]

QUOTE: "a decision to use any metal fitting on a metal boat incurs a number of extra steps to really, properly isolate them from the hull. "

I'm serious about the aluminum anodes on my steel boat. 14 plates as big as license plates, plus a collar around the prop shaft. My bronze through hulls are not isolated from the steel. Nothing below the waterline corrodes. When I started out, I had them isolated, but the extra layer of material (plastic) created problems while simply keeping up with the anodes (silver test lead, replace when below one volt) solved the problem.

[Scubaseas]

HDPE is fine underwater.

Marelon has zero galvanic potential. If you have a steel boat a silver chloride half cell to check galvanic action might be a good thing to own. I bought one from boatzincs.com. No relationship other than a happy customer

[Cheechako]

Those expensive SS valves look in pretty good shape. If they are one wonders "if it ain't broke...." But make sure they aren't "living well" because the hull is sacrificed!

[Clivevon]

Hi. Check out Trudesign seacocks from New Zealand. I have 10 of them without any issues for 6 years. Perfect. No corrosion issues of course.

[raahell]

Thanks all, for the comments and suggestions.

Cliveon: Trudesign seacocks look great but they are hard to source in Canada. Marelon Full Flow seacocks (with the wide bases) are very similar and more readily available.

Scubaseas and Tkeithlu. Great points about sacrificial anodes and determininig how well they are protecting the hull. My sailboat has 6 anodes on the hull, 3 on the swing keel, 2 on the rudder and 1 on the shaft. They're not licence plate sized but still fairly substantial teardrop or sphere shapes. That seems pretty good to me but a silver chloride half cell will tell me if I'm over/under protecting the hull.

Cheechako: I do intend to dismantle those SS thruhulls and check for pitting of the inside SS surfaces and/or steel plating. If I see any I will go with the Marelon's there too. If not than I will make washers from my HDPE sheet to better isolate them when I reinstall them.

In the meantime I managed to clear away enough cabinetry to zip cut the welded steel piping on all thruhulls and can now start getting things ready for the Marelons. Which brings me to another question. The hull is 3/16" thick. Does it make sense to weld a 1/8" thick doubler plate to the inside of the plating? This will ensure perfectly flat mounting surface, adds strength at a critical point and also adds material where corrosion is most likely to happen. I have a MIG welder so this will not be too hard to do.

[bcboomer]

rahell

Trudesign are available from:
https://victory-products.com/pages/s...ign+ball+valve

This is the Canadian distributor. They can probably direct you to a dealer in Ontario where you might get them a little cheaper. I know that locally Steveston Marine sell them at a discounted price.

I've had mine for 7 years and they are terrific. No corrosion worries and they never seize up. Marelon have a long history of requiring frequent operation to avoid seizing. Nothing so much fun as having the handle break off a Marelon valve that 2 weeks ago was working fine.

[Compass790]

Originally Posted by raahell

Thanks all, for the comments and suggestions.

Cliveon: Trudesign seacocks look great but they are hard to source in Canada. Marelon Full Flow seacocks (with the wide bases) are very similar and more readily available.

Scubaseas and Tkeithlu. Great points about sacrificial anodes and determininig how well they are protecting the hull. My sailboat has 6 anodes on the hull, 3 on the swing keel, 2 on the rudder and 1 on the shaft. They're not licence plate sized but still fairly substantial teardrop or sphere shapes. That seems pretty good to me but a silver chloride half cell will tell me if I'm over/under protecting the hull.

Cheechako: I do intend to dismantle those SS thruhulls and check for pitting of the inside SS surfaces and/or steel plating. If I see any I will go with the Marelon's there too. If not than I will make washers from my HDPE sheet to better isolate them when I reinstall them.

In the meantime I managed to clear away enough cabinetry to zip cut the welded steel piping on all thruhulls and can now start getting things ready for the Marelons. Which brings me to another question. The hull is 3/16" thick. Does it make sense to weld a 1/8" thick doubler plate to the inside of the plating? This will ensure perfectly flat mounting surface, adds strength at a critical point and also adds material where corrosion is most likely to happen. I have a MIG welder so this will not be too hard to do.

Its standard practice to put a compensating plate on any welded tank penetrations if you want to avoid weak points so yes a doubler plate is a good idea,
Grizzled old boatbuilder next to club slipway told me he has way less trouble with FRP thru-hulls & seacocks than metal so good choice the marelon. Don't tell anybody but we even have some CPVC ball v/v's on ours.

I'd be ok with the 316 ball v/v's tho.

[EngNate]

Yes, it's possible to isolate with the sealant, but not reliable. Each penetration gets a bushing and two washers, Delrin is best, it's like super-nylon. I see HDPE starting to break down after 10 years, sooner when exposed to sunlight. It isn't that strong and is not available thin. Delrin material and hardware is available from industrial suppliers. McMaster-Carr is a good one in the US. Go thin - 1/16". The rubber washer with the transducer is provided for sealing.

Yes, doubling up at all penetrations is standard practice I would follow. And, all in all, the composite seacocks are your best solution for non commercial, not high breakage risk. Pretty much all plastic/composite valves are sticky, so two recommendations for one that isn't I'd check them out.

The bronze thru hulls on steel with no problem: Remove one say 10 years after and examine the area that's now concealed. It's not a great big thing because there is lots of steel and only a bit of bronze, but the penetration will get enlarged and there will be pitting around the edge of the flange.

[raahell]

I can order directly from Victory Products, according to an email I rec'd from them.

I priced out 4 x 3/4" and 2 1-1/4" seacocks and fittings in both Marelon 90 series and Trudesign w/ load bearing collars. Turns out that the Trudesigns are only $60 extra for the lot, so I think I'll go with Trudesign based on the comments I've rec'd. Thanks!

We already have one new Marelon 90 series 3/4" seacock (pic, in case anyone is confusing the 90 series with the more common triangular base Marelons) which I can't return so I'll install just this one, along with the Trudesigns. This will give me an opportunity to evaluate how the two compare, on the same boat, under same usage conditions. I'll ensure to install the Marelon in the easiest-to-get-to location

[bcboomer]

rahell
Just for fun try Marine Outfitters. They carry Victory products and may be cheaper than directly from Victory. (Victory sticks to a MSRP that is often more than the dealers sell them for)

[raahell]

Hi bcboomer,

I've subscribed to all the Canadian marine chandleries for one thing or another. Marine Outfitters in ON does carry some Victory products but if they sell Trudesign they're hiding it pretty well as there's nothing on their website. Marelon, definitely. The Binnacle in NS also doesn't stock Trudesign. The only Canadian store (that I've found) that stocks and advertises Trudesign online is Steveston Marine in BC but they don't list all the sizes. This is why I'm happy to see that Victory will sell directly, as they seem to carry the full range of sizes, as well as the many pipe fittings and other bits also made by Trudesign.

If anyone has a Canadian source other than Steveston and Victory for Trudesign, let me know and please add a link, don't just claim that it exists. Thanks!

[George_SD]

Personally, I would remove them and replace with anything (Marelon or Bronze) specifically designed for the purpose. Correct sizing, sealing, installation technique, etc.