Composite vs Bronze Seacock

[Randall Schmidt]

I have a 1984 O'Day. When I got it just over 10 years the seacocks were frozen. They were bronze. I replaced them with Marelon composite as they were recommended by my boat yard. One is failing now. The raw water input valve is stuck open. Should I go back to bronze? I'd like to get the seacock in advance of haul-out. What I find online is this: 3/4" bronze flanged seacock (NPS thru-hull / NPT hose side). https://defender.com/en_us/groco-fbv-series-full-flow-flanged-ball-type-seacock. GROCO FBV‑750 Tri‑Flange Bronze Seacock · $57.99. ChatGPT tells me I need to measure the hose and most are 3/4" inside diameter but could be 1" which will change what I need. I hate to wait to order. Maybe local west marine keeps these in stock?

 

[JoeWhite]

My 1999 C36 Marelon valves and thru-hulls have never given me any problems.
If the valve is in the open position, there may be debris inside the valve preventing it from closing.
Can you disconnect the hose from the strainer and hold it above water level, then blow into it, or force water in from shore water using garden hose or use a wood dowel to remove the restriction. Do not force closing it as it may start to leak.
My raw water valve is straight through. If yours has an elbow on the top you may not be able to use a dowel.
You may be able to dive down and try to remove the restriction.

 

[jssailem]

Randal... You are listed as being in Sterling, VA. If the boat is nearby, I suspect it is a bit chilly either in the Potomac or the Chesapeake.

Both the Marelon and the Groco through hulls will work. @JoeWhite shares some good info as to the possibility of clearing the valve. I have used the air technique, and it has yielded a 75-80% success rate for me. Worthy of a try. I have used a vacuum cleaner by blowing air through a hose. It is an easy way to try to clear out stuff. Your Marelon valve should have used a similar material for the through hull. Check its condition before you apply pressure to try to close the valve. The Marelon valve passed the ABYC standard for usage below the waterline on boats.

When you can swim below the boat, one technique is to have a diver push a plastic bag into the through-hull to stop water so the valve can be repaired. The bag reduces the fear of sinking.

 

[dLj]

It's really up to you. Both should work. How did you service the current thru-hull? Perhaps there is something there that may need addressing?

dj

 

[Ralph Johnstone]

I replaced them with Marelon composite as they were recommended by my boat yard. One is failing now. The raw water input valve is stuck open.

Never heard of a Marelon valve failing or binding. The big question is "Do you exercise them on a regular basis ?" It certainly won't hurt them and it may keep them free from binding.

Seeing how this may be the only Marelon valve sticking and the water is bloody cold in your neighbouthood, try heating the valve body with a hair dryer (or a heat gun if your adventurous.) Just do it slowly until the valve feels warm to the touch and then see if it moves without applying a gawdawful force.

I just hate to see the waste of a Marelon valve.

 

[colemj]

Which Marelon valve? Forespar makes one that is notorious for sticking and the handle breaking off. These should never be used on a boat. They shouldn't ever be sold either, but Forespar suckers people on the price.

Forespar also makes an excellent Marelon seacock that they used to only sell to OEM builders, but now sell widely. It is the OEM-93 series.

Pictures of bad and good choices attached.

An alternative that I like better than the Forespar 93 series is the ones by TruDesign. They not only have a better way to attach to thehull, they also have a teflon bearing housing for the ball that stays easy to use without any additional maintenance.

Mark

BAD:

GOOD:

 

[LakeOntario270]

I have a 1996 Catalina with the "Good" Marlon that was stuck once. While on the hard for winter I removed the 4 screws to disassemble the unit. I cleaned the insides with some spray bathroom cleaner, lubricated the inside with some Marlon lube oil from Catalina Direct, and then reassembled. The valve then worked perfectly fine.

 

[FastOlson]

Some clarification might be in order. Forespar purchased the RC Marine line of Marelon sea cocks and valves sometime in the late 80's or very early 90's. They then re-designed the tooling to produce their "93" line of valves. Our '88 boat was built with all RC Marine sea cocks, and due to them all sticking (evidently the ball material was slightly hydoscopic and expands a smidge with immersion) I decided to changed them out.
You can keep them working OK, but do need to exercise them regularly and apply a proprietary lube.

I replaced all the OEM "RC" valves in the mid 90's with the updated ones from ForeSpar. Only one of them broke a handle - way over a decade later. Our prior boat had bronze ball valves and I liked them just fine, but did have some concern about visiting any "hot" marina and having the metal quickly be eaten away as has sometimes happened to other boaters.

There are no perfect answers, just compromises we all choose to live with , IMHO.
Note that the later/current ForeSpar 93 model sea cock can change out a valve with the thru-hull base part still in place, and this can be done with the boat in the water.

 

[Captain Larry-DH]

Note that the later/current ForeSpar 93 model sea cock can change out a valve with the thru-hull base part still in place, and this can be done with the boat in the water.

Yup. That white cap installed on the side of its body is a plug that can be stuck in to cover the hole from outside the boat.

 

[Captain Larry-DH]

@Randall Schmidt if you do change to bronze, be aware that (for the same ID) the hull hole diameter of the Marelon fittings is larger than the hole required for the bronze fittings. For example, a 3/4” ID thru-hull fitting has a larger OD in Marelon than in bronze. So check your measurements before you buy to make sure it will fit properly. Too much slop in the hole might lead to loosening, and you should not depend on the sealant to provide the mechanical bond. (Yes, 5200 would be up to the task but I hate when people use that for fittings that might eventually need replacing. IMHO it should not ever be used for thru-hulls.)

 

[Project_Mayhem]

@Randall Schmidt Pulling the boat out for maintenance and repair would be the best option. My suggestion below wont work while the boats in the water. I'm not sure how much risk your willing to take but I have an idea. You can disassemble the valve for service. I think if you were to loosen the top of the valve a turn or so, it might relieve some pressure on the o-ring and valve just enough for you to turn the valve handle. However, if you loosen the top of the valve too much, you'll have a whole lot of water coming into the boat. Loosen a little bit at a time is the obvious choice should you try this.

I think the marelon valves use a tapered thread. The through hull on my 78 ODay 25 had a straight thread with a $50 Groco ball valve. That ball valve lasted 47 years before I replaced it due to pitting on the ball. I'm in lower Lake Michigan.

Never heard of a Marelon valve failing or binding.

Mine will be difficult to operate if not excersised on a regular basis. I suppose some lube would help

 

[capta]

I've owned and sailed boats built in the early 1900s with bronze seacocks. They worked perfectly well at 60 to 80 years old.
It is all about knowledge.
A real "seacock" has a tapered shaft with a hole in to let the water through. These are NOT ball valves. After loosening what ever is holding the tapered shaft in (nut/wing nut, etc.) it can be removed and then the whole unit is easily cleaned. Before replacing the tapered shaft, one should get some lapping compound and use the tapered shaft to mate well in the housing. It does take some time and effort. On some, Perko I believe, once the seacock is open or closed, the nut can be tightened so that the position cannot accidentally be changed, another thing the plastic thru hulls do not have. The hole in the tapered shaft is fairly sharp and should cut many things that might prevent the seacock from closing.
If this is your "forever" boat it may be worth the cost of going back to bronze seacocks (unless you saved the old ones), however, if not, then perhaps go with plastic. I would never use or suggest ball valves.

 

[marcham]

I have a 1984 O'Day. When I got it just over 10 years the seacocks were frozen. They were bronze. I replaced them with Marelon composite as they were recommended by my boat yard. One is failing now. The raw water input valve is stuck open. Should I go back to bronze? I'd like to get the seacock in advance of haul-out. What I find online is this: 3/4" bronze flanged seacock (NPS thru-hull / NPT hose side). https://defender.com/en_us/groco-fbv-series-full-flow-flanged-ball-type-seacock. GROCO FBV‑750 Tri‑Flange Bronze Seacock · $57.99. ChatGPT tells me I need to measure the hose and most are 3/4" inside diameter but could be 1" which will change what I need. I hate to wait to order. Maybe local west marine keeps these in stock?

Do you open and close each seacock monthly? If you don't, it doesn't matter what you buy, it will fail. I'd stick with plastic.

You can replace the seacock without replacing the thru hull. I've seen it done in the water with a diver.

 

[JamesG161]

I chose bronze by GROCO.

MaineSails link

On how to install them.

Jim...

 

[Ward H]

If purchasing OEM Series 93 valves, be aware that the common thread found on these valves is different from most other valves.
The OEM Series 93 Ball Valves have what Forespar calls Buttress threads. These are different from the NSPM threads found on their other valves and fittings. Forespar pre packages the valve and thru hull together to ensure users do not try to install a Series 93 valve on a NSPM threaded thru hull as the threads do not work together.
You can special order the Series 93 Valves with NSPM threads through your supplier.
You can also order the valves with BSP threads.

I close my valves whenever I leave the boat and open them as needed when I return. While a couple might be a little harder to open at times, exercising them solves the issue. Forespar also sells a lube for them that works pretty well.

 

[Project_Mayhem]

I may have to eat my words. I pulled one Marelon valve the other day that was difficult to operate even after using some silicone spray on it. There was also no obvious way to disassemble it. The one for my galley sink on the other hand came apart with no issues. I'm still not a fan of plastic through hulls. Seems far too easy to break when a valve and plumbing fittings can act as a lever

 

[colemj]

I may have to eat my words. I pulled one Marelon valve the other day that was difficult to operate even after using some silicone spray on it. There was also no obvious way to disassemble it. The one for my galley sink on the other hand came apart with no issues. I'm still not a fan of plastic through hulls. Seems far too easy to break when a valve and plumbing fittings can act as a lever

"Plastic" is covering a lot of ground here. In the case of Marelon, it is glass fiber reinforced composite polymer, and not just some ABS stuff. It will not break when levered as it is intended to be installed. My experience is it will not break when levered even if the lever arm starts at the top of the threads. It is very strong stuff.

Similarly, "metal" covers a lot of ground, and one wouldn't conflate a cheap brass one from Walmart with a good bronze one from Buck Algonquin.

Silicon spray shouldn't be used on these. The solvent carrier can swell them. Use Superlube (solid, not liquid version).

Mark

 

[Project_Mayhem]

Silicon spray shouldn't be used on these. The solvent carrier can swell them. Use Superlube (solid, not liquid version).

Thank you for the tip!

 

[FastOlson]

After I had changed out our original RC Marine marlelon valves, a boat builder told me that he always found that he could restore rotation to the mid part that clamps the ball by Slightly (!) backing off the large nut on one end or the other. I did not try that and the yard had already disposed of the old valves. Note that the large nut on each end clamps the ball in the center section, so he certainly might have been right. I have never confirmed this, tho.
(Filed under odd 40 year old trivia...)