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Old 05-14-2021, 05:57 AM   #1
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Restoring Old Unique Thruhull Fittings

My 1981 Grand Banks 36' Classic Trawler has several unique thruhull fittings that are showing surface corrosion and discoloration on the copper(?) tubing and entire fitting.
Finding replacements has proven impossible. Is there a way to restore these unique thruhulls? I have been considering using epoxy and fiberglass cloth on the tubing to protect and restrengthen it.
Has anyone encountered similar problems and come up with solutions?
Thanks
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Old 05-14-2021, 07:58 AM   #2
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Do you have a picture?
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Old 05-14-2021, 09:14 AM   #3
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Sorry to say but, if the through hull valves are unique, give serious consideration to replacing all of them with common, up to date through hull valves. Dont forget to bond them.
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Old 05-14-2021, 09:47 AM   #4
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Depends upon what you mean by corrosion and discolouration.
It is absolutely normal for copper based alloys to darken and/or go green over time.
The verdegris can be removed with some effort but it will come back, maybe slowly. THese fittings are usually of heavy construction and of good quality alloys, real BRONZE, which can withstand decades of existence in seawater.

BUT, for any through hull it is not the outside that is of concern, it is the inside of the fitting which is where the seawater will have its effect.

As far as tubing goes then I am a bit more skeptical as tubing is thin walled and may not be one of those alloys. Tubing can be subject to vibration caused cracking. Depending upon the specific tube alloy they can become subject to water erosion at bends mostly which will weaken then from material loss.

What is the tubing used for? Fuel, fresh water and hydraulic steering lines. THen the biggest problem for those is not being secured well enough allowing vibration.

As far as fiberglassing a through hull I would not waste my time and ,I think, it is a time waster. Worse any covering may hide any signs of degredation that you SHOULD be aware of.

Keep them clean of loose verdegris and check them. If leaks/weeps are appearing then they may simply need a resealing to the hull, hoses and of service of the working parts at haul out times.

I don't have your boat but mine is a 77/78 and the original through hulls are still in use. I have added some over the years for extra equipment but those originals show no distress.
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Old 05-14-2021, 09:56 AM   #5
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Quote:
Originally Posted by OldDan1943 View Post
...............Dont forget to bond them.
What if they were not bonded the past forty years? Or if they were did it help.
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Old 05-14-2021, 10:31 AM   #6
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C lectric's advice above is spot on. Those old thruhulls are probably tapered plug types and the following article shows you how to lap them and make them good as new.

https://marinehowto.com/servicing-ta...cone-seacocks/

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Old 05-14-2021, 10:46 AM   #7
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What if they were not bonded the past forty years? Or if they were did it help.
My experience, makes the zincs last longer.
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Old 05-14-2021, 11:35 AM   #8
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Me thinks we really need pictures to advise. Plead post. :-)
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Old 05-14-2021, 12:55 PM   #9
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I would proceed carefully with the caveat that restoring old seacocks is generally not a inherently prudent practice. Why take any chances on a thru hull penetration with so much at risk ? I’m assuming these are seacocks as that is all I’ve ever seen on older GB’s

I can pass on some info about early American Marine’s seacocks and some other bronze fittings. They, Hans Christian, and quite a few early Kaohsiung builders used these generic Groco style bronze seacocks. No markings but from a distance you’d swear they were Groco’s. They weren’t, and were lab tested and found to vary in alloy from typical manganese bronze (30-35% Zn ) to plain old brass with 35-45% Zn. Many leaked raising red flags as quite a few of these boats were essentially new. We found the bodies were often bored off center or out of round, you name it. Some were packed full of a black bedding compound product to stop leakage. You get my drift. Anyway an on-site ex-pat hull inspector named Tuthill found the source of these valves. A company affiliated with Chang Iron was melting down brass, copper and bronze anything similar and selling it to one or two small Taiwanese foundries who were supplying seacocks and other ‘bronze’ fittings.

American Marine and Hans Christian and many others cleaned up there act in the very late 70’s and 80’s and changed to WC, Groco and even Blake sea valves. From about the mid 80’s on all GB’s were delivered with WC ball types. In a couple of the yards I worked in there was a notice posted that early GB’s and about dozen other makes should have the thru hull valves removed, inspected and replaced as needed. Of course most yards sold new valves but importers were picking up the tab so new Groco’s it was.

So I digress as usual but if your seacocks ( tapered cone plug type ) have no markings on them I would suspect them. They could be high in Zn so not a true bronze and susceptible to dezincification. Bronze will ring like a bell when tapped with a hammer though a valve may not due to shape. If they are dezincing you can often carve the flange with your knife or break off a piece with a crescent wrench. The faying or mating surfaces of the valve body and tapered plug should show absolutely no porosity or pits. Take your pocket knife and try to shave the edges of the rectangular plug passage hole. If it’s soft you’ll know it.
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Old 05-14-2021, 03:21 PM   #10
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Generally tubing isn’t used on a through hull but instead hose is used. If there is copper tubing going to a through hull, I would probably replace it with a quality hose. The through hull itself is another issue. If they are in good condition they may be able to be cleaned up and refurbished. However if they are suspect then change them out, do not try to fiberglass them. You are asking for trouble that way.
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Old 06-13-2021, 11:10 PM   #11
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i have a 1987 chb, what can you tell me about what service my thru hulls need on a regular basis ?
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Old 06-14-2021, 01:34 AM   #12
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[Edited to add: I can't imagine a situation in which fiberglassing a deteriorating metal tube that's part of a seacock would be a good idea for preventive maintenance, and agree with others above that I'd like to see a photo.]

I'm all for re-conditioning something like the Spartan bronze tapered (bronze) or Wilcox Crittenden seacocks.

However, many of the tapered cone type seacocks I've seen on GB's are the type where the "cone" is actually a rubber plug (one clue is there are two "handles" - one looks like a thin rod).

I had the genuine Groco version ("Groco SV") of these (rubber plug type) seacocks on a boat in the early 2000's, and even then it was nigh on to impossible to replace the rubber plugs (found a few 3/4" size on a dusty shelf). They aren't as potentially long-lived as a true tapered bronze cone such as the Spartans, IMO.

If you have those (or as mentioned above, an impostor version), I would replace them if they are looking dodgy (given that you can't easily get parts, and/or if they are inferior metal).

I have some older Spartan bronze tapered cone seacocks, and they are very robust and re-conditionable, generally. A nice seacock, IMO.

PS: I once owned a boat built by a reasonably respectable builder wherein the original engine intake "seacock" was a copper tube pushed out through the hull, after which a washer was placed on the outside of the hull and then the tube peened over. What could possibly go wrong.

Also: Groco SV datasheet:
Attached Files
File Type: pdf Groco SV series rubber plug seacock.pdf (54.0 KB, 5 views)
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Old 06-14-2021, 08:15 AM   #13
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mine have just one handle

Quote:
Originally Posted by Frosty View Post
[Edited to add: I can't imagine a situation in which fiberglassing a deteriorating metal tube that's part of a seacock would be a good idea for preventive maintenance, and agree with others above that I'd like to see a photo.]

I'm all for re-conditioning something like the Spartan bronze tapered (bronze) or Wilcox Crittenden seacocks.

However, many of the tapered cone type seacocks I've seen on GB's are the type where the "cone" is actually a rubber plug (one clue is there are two "handles" - one looks like a thin rod).

I had the genuine Groco version ("Groco SV") of these (rubber plug type) seacocks on a boat in the early 2000's, and even then it was nigh on to impossible to replace the rubber plugs (found a few 3/4" size on a dusty shelf). They aren't as potentially long-lived as a true tapered bronze cone such as the Spartans, IMO.

If you have those (or as mentioned above, an impostor version), I would replace them if they are looking dodgy (given that you can't easily get parts, and/or if they are inferior metal).

I have some older Spartan bronze tapered cone seacocks, and they are very robust and re-conditionable, generally. A nice seacock, IMO.

PS: I once owned a boat built by a reasonably respectable builder wherein the original engine intake "seacock" was a copper tube pushed out through the hull, after which a washer was placed on the outside of the hull and then the tube peened over. What could possibly go wrong.

Also: Groco SV datasheet:
mine appear to be bronze and are all connected to a ground. a couple are very stiff and difficult to open and close. what would i need to do to remedy that ? i do not know what the process is for freeing up sticky valves.
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Old 06-14-2021, 06:11 PM   #14
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mine appear to be bronze and are all connected to a ground. a couple are very stiff and difficult to open and close. what would i need to do to remedy that ? i do not know what the process is for freeing up sticky valves.
I see you are not the OP and it sounds like you have general questions about your seacocks. Since I (and maybe others) don't know what you have, can you post a photo? And/or a brand and model? Recommendations can be different for different types (ball, cone, etc.) Or the recommendation could be "change that!" but it all depends on what you have now.
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Old 06-14-2021, 06:32 PM   #15
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I had the "plastic" hull valves. It is my theory that over time they will become brittle, I'd break the handle off at the most inopportune time so, when I went to the yard, I had them all changed to Groco hull valves. I had a couple 1/2 inch hull valves I changed to 3/4 inch too. Each time I go to the yard I have them serviced per Groco's recommendation. Also I cycle them open and closed once a month. Yes they are all tied into the bonding system.
Groco hull valves and strainers seem to be the current boating standard.
So my recommendation is, next time you go to the yard, change the hull valves over to Groco ball valves.
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Old 06-15-2021, 05:37 AM   #16
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The old Groco SV were fine BUT most owners never read the instructions,and attempted to rotate the valve with out first taking the pressure off,,,


Personally I do not trust the modified house plastic ball valve as marine growth can cause them to seize.The SV can be loosened enough to be turned with growth , but the best of all is the bronze tapered plug units , that can be easily maintained for a century.


91999 GROSS MECHANICAL LABORATORIES, INC. ALL RIGHTS RESERVED.For service assistance/information call 410.604.3800 and ask for Seacocks Service Department. After hours, go to www.groco.net.Info Sheet SV Series, 1 of 1000401SV Series Seacocks Maintenance, Parts and AssemblyThe Concept: GROCO SV series seacocks were manufactured for the marine industry between 1960 and 1993. Production was discontinued in favor of the presently manufactured BV, SBV, and SBV-P series Full Flow Ball Valves


.SV series seacocks operate on the simple “expanding plug” principle. Awingnut on the back of each valve is hand-tightened when in the valve is in the desired open or closed position. Tightening the wingnut expands the rubber plug, thus sealing the valve.Operation: When a change in valve position is desired, the wingnut is loosened enabling the operator to turn the valve handle to the new position. Re-tighten the wingnut each time.
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