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Old 12-08-2016, 07:07 PM   #1
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Thru Hull & Sea Cocks

I have been doing a trawl through the forum archives as i need to replace the Thru Hull fittings on the boat as they are about 30 years old and very stiff to operate.There is some good advice there, but a few questions remain.

The origional fittings are brass & there seems to be a move to using Marelon (Forespar) these days. Just wondering if anyone has gone that path?

Also, I understand the Kiwi's are making a similar product through a company called Tru design, a composite material with a ball valve, although I have always understood that ball valves are a no no for sea cocks.

As I have nine through hulls to replace I certainly want to get this right, so if anyone has experience of these options I would be glad of your advice.

Cheers.

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Old 12-08-2016, 07:13 PM   #2
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Greetings,
Mr. AG. Are the fittings BRASS or bronze? If indeed brass, get them out of there! If bronze, I would suggest a rebuild and re-install to cure the stiffness. I really don't like ball valves or plastic materials as seacocks.
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Old 12-08-2016, 07:15 PM   #3
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Marelon thru hulls and seacocks are fine, but they do need to be exercised relatively frequently or they can be come very stiff. They are not a strong as bronze but they do eliminate corrosion problems.

My material of choice is an all bronze seacock. Groco is acceptable but I prefer Conbraco. Virtually all seacocks now have ball valves. The best ones have chromed bronze balls in the valves.
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Old 12-08-2016, 07:35 PM   #4
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Our last boat built in 2005 has Forespar Marelon seacocks and thruhulls.
They are easy to live with, just about as close to maintenance free as anything on a boat can be.
Our previous boat, a 1982 Able Whistler 32 needed the seacocks replaced and I used the Forespar Marelon seacocks there too, the same OEM series that manufacturers use.
American Tugs are made with the same valves.
Mose chandleries can get these for you, at least I've always been able to get them...
Bruce

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Old 12-08-2016, 07:52 PM   #5
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Quote:
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Our last boat built in 2005 has Forespar Marelon seacocks and thruhulls.
They are easy to live with, just about as close to maintenance free as anything on a boat can be.
Interestly enough, my 2005 sailboat also has Marelon seacocks. They are still great. I regularly open and close the raw water intake for the engine, and the raw water intake for the heads. They have held up wonderfully and I wouldn't mind having them again. On the rare occasion that the boat gets hauled, I use some grease to lube them. This has only happened about 4 times total in the past 6 years I have owned the boat.

Marelon is not good for a valve that you just leave in the open or closed position for long periods of time. However, I would imagine that bronze valves should be exercised periodically as well.
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Old 12-08-2016, 08:05 PM   #6
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I'm not sure where the idea that you must move Marelon or it sticks comes from.
The cockpit drains on our Sabre are 1 1/2" Forespar Marelon valves that get closed annually, just to make sure that they work. They still move as easily after 11 years as they did when new. I bet that they have not been moved more than 11 times in their life!
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Old 12-08-2016, 08:24 PM   #7
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I am sure your doing the whole thing and not just the valves. Did our 9 last year. All groco and all Bronz.
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Old 12-08-2016, 09:10 PM   #8
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If you've searched the archives, you've probably come across the Compass Marine how-to's on seacocks. Here's one and there are several others on the CM site.

Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine How To at pbase.com

I found them invaluable as we replaced the 13 below-the-waterline seacocks and throughhulls on our boat.
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Old 12-08-2016, 09:45 PM   #9
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Next time boat is on the hard, scrap the paint off the through hulls. Should be a nice bronze color. If they are pinkish, the through hulls have to be replaced. If they have been in there 30 years they may have to be cut out.
Next issue is the valves. If they are tapered type, you can disassemble them and lap fit them. They should be good for another 30 years. If they're ball type, I'd just replace them.
If both through hulls and valves need to be replaced I'd price out bronze and marelon. Marelon has been around a long time and is equal to bronze but with a lot less maintenance.
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Old 12-08-2016, 10:46 PM   #10
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Bear in mind that I sell seacocks when you read what follows.

If your seacocks are thirty years old they are not brass, they are bronze.
Just because they are stiff is not a reason to replace them. Most seacocks can be serviced and good ones should last the life of the boat.

We can give you better advice if you let us know what kind of seacocks they are and maybe post a picture.

If you do decide to replace, I'd love the chance to quote you on them.
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Old 12-09-2016, 12:31 AM   #11
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What are the negative issues with a ball valve sea cock?

What is better than a ball valve?

Had an older boat with a gate valves, replaced them with ball valves.
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Old 12-09-2016, 01:32 AM   #12
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Nothing wrong with flanged ball valve seacocks.

The problem is that a lot of people screw a regular ball valve, with out a flange, onto a thru-hull fitting and call it a seacock. That is a weak setup. The thru-hull is not supported and can break. The other problem is that the thru-hull has straight threads and the ball valve will have tapered threads. This makes a weak connection.

Gate valves screwed onto thru-hulls are even worse because most of them have brass stems that have a very limited life in salt water.
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Old 12-09-2016, 11:19 AM   #13
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Quote:
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I'm not sure where the idea that you must move Marelon or it sticks comes from.

Both my personal experience and Forespar's own recommendations.
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Old 12-09-2016, 11:32 AM   #14
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Both my personal experience and Forespar's own recommendations.
Interesting.
Ours were dangerously difficult to get to before I installed the generator and moved the water heater. Afterword it was relatively easy.
They never showed the slightest tendency to stick. I wonder what makes some stick and ours not?
Curious...
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Old 12-09-2016, 11:33 AM   #15
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Quote:
Originally Posted by HopCar View Post
Nothing wrong with flanged ball valve seacocks.

The problem is that a lot of people screw a regular ball valve, with out a flange, onto a thru-hull fitting and call it a seacock. That is a weak setup. The thru-hull is not supported and can break. The other problem is that the thru-hull has straight threads and the ball valve will have tapered threads. This makes a weak connection.

Gate valves screwed onto thru-hulls are even worse because most of them have brass stems that have a very limited life in salt water.
Thanks for your reply.
Completely agree with your point about the flange.
Thought I might be missing something out there that was better than a ball valve.
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Old 12-09-2016, 11:42 AM   #16
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I have used all three of the main types of marine seacocks with similar success: tapered cone, ball valve and Maralon. I like tapered cone the best because you can refurbish them by lapping the cone in with lapping compound and it then seals as good as new. Maralon are ok, but as noted above, they will stick and need to be exercised regularly. Ball valves are also good, but make sure that you use bronze ones and use a straight thread on one side to screw into thru hull fittings. Or you can use a fairly new fitting- the Groco flanged seacock adapter that mates up to tapered ball valve threads.

Pbase has several photo essays on seacock installation and maintenance- Welcome To MarineHowTo.com Photo Gallery by Compass Marine How To at pbase.com

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Old 12-09-2016, 01:51 PM   #17
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Originally Posted by angus99 View Post
If you've searched the archives, you've probably come across the Compass Marine how-to's on seacocks. Here's one and there are several others on the CM site.

Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine How To at pbase.com

I found them invaluable as we replaced the 13 below-the-waterline seacocks and throughhulls on our boat.
Compass. Marine also has a How To article on reworking bronze tapered plug seacocks if that what you have.
If so and they are otherwise in good shape I'd consider reworking them.
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Old 12-09-2016, 03:29 PM   #18
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What are the negative issues with a ball valve sea cock?

What is better than a ball valve?
Yeah. I have the same question too. What's wrong with a ball valve?
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Old 12-09-2016, 04:43 PM   #19
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My boat came with 5 Marelon (Forespar) thru-hull seacocks. I ended up removing all of them. They weren't through bolted and disassembling the through hull portion to verify integrity proved destructive on a couple. Removed 3 (reglassed hole) and replaced 2 with through bolted bronze Groco seacocks.

The Forespar is a decent product but removing the seacock to verify integrity was an issue. While I may never remove my bronze ones again, I felt for piece of mind it was important to verify proper installation. The design is such that disassembling the ball portion is but 4 screws. The seals are 3 orings and 2 gaskets. Contacted Forespar about replacement orings and gaskets. You would have thought I had disassembled a nuclear reactor that was running. Apparently you need to be a qualified technician to work on one. They didn't want the liability of selling me the parts, so they gave them to me including free shipping. The base of the valve was destroyed trying to remove it from the through hull tube. Knew I wasn't going to be able to replace that part, so replaced with bronze. Really sad part is that you could have an essential good as new valve by replacing the orings and gaskets every 5 to 10 years.

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Old 12-09-2016, 08:48 PM   #20
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My insurance would not cover tapered. We had to switch.��
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