Marelon Seacock fail!

[Hayden Watson]

I replace all 4 of my Marelon thru-hull / Marelon ball values during my haulout for bottom paint. The originals were 32-years old and were ball value on thru-hull with no flange to support the torque from working the valve.
I installed them per instructions using 5200 under the mushroom head and in the threads that go through the hull and used Teflon tape for the full hight of the threads into the body of the seacock.
I launched today and after getting back to my slip, 3 out of 4 of them began to leak. One is just moist around the base with a drip running down the hull every 10-15 minutes. The other two have a drip run out of the base of the seacock at a rate of several drips per minute. Before this haulout I would not even noticed these leak but I also installed a Lastdrop seal and it is working perfectly so my bilge should still be bone dry like it was this morning but now I have an inch in the bilge and I expect my bilge pump to run once or twice a day due to the new upgraded seacocks.

 

[jssailem]

Could it be the Teflon tape?

 

[jssailem]

Install instructions call for bedding materials but not Teflon on the threads of the nylon material.

Marelon Thru Hull Sea Valve Installation

Marelon® is a proprietary formulation of polymer composite compounds using composite glass and/or carbon fiber reinforced polymers and additives to produce a superior marine-grade product. For use above and below the waterline

www.forespar.com

 

[dLj]

Can you tighten down the sea cock valves? From your description, I would agree with John, I think more likely your teflon tape section may be the culprit. I would not have used teflon tape in that application. I'd have used a liquid sealant compatible with the materials you are using.

dj

 

[Ralph Johnstone]

The other two have a drip run out of the base of the seacock at a rate of several drips per minute

Teflon tape in the valve threads may well be the source of your problem.

Based on numerous years of being around high pressure threaded joints in refineries, myself and many others long ago found that teflon tape is NOT the screaming hell it's supposed to be.

Its popularity is based on the fact that "it makes a nice clean joint". It's much cleaner than paste sealants. Unfortunately, it's more likely to leak compared to paste sealants. The present practice for a near 100% perfect joint sealant is considered to be a light smear (applied CCW) of paste sealant over teflon tape (applied CCW) coated threads. The thought is that the teflon supplies the bulk of the sealing while the paste further seals up any possible discontinuities in the tape.

The one place where teflon tape does work well on its own is threaded steam fittings. The teflon is thought to soften somewhat and slowly flow into discontinuities. Teflon tape is regarded as a poor choice on cold water joints.

Looks like the odds beat you on your refit job. Are you sure you applied the tape CCW ? Greater probability of leaking if applied CW.

 

[Hayden Watson]

Install instructions call for bedding materials but not Teflon on the threads of the nylon material.

Marelon Thru Hull Sea Valve Installation

Marelon® is a proprietary formulation of polymer composite compounds using composite glass and/or carbon fiber reinforced polymers and additives to produce a superior marine-grade product. For use above and below the waterline

www.forespar.com

Per the Installation/Maintenance tab for Marelon Flange Mounting Seacocks.
"Now you’re ready for sealant. You can use an aggressive sealant/adhesive here (like 3M 5200) as you should not need to remove the thru-hull again. Do not use this aggressive sealant on the threads going into the valve however. Use Teflon tape or other removable sealant on the threads to valve connection. Follow all instructions from the sealant manufacturer for proper surface prep and use. Read carefully the cure times required."

 

[thinwater]

Since the valve has not failed, the title is poor.

 

[Hayden Watson]

Teflon tape in the valve threads may well be the source of your problem.
...
Looks like the odds beat you on your refit job. Are you sure you applied the tape CCW ? Greater probability of leaking if applied CW.

Yep, CCW. I hold the tape on my pinky and the fitting on thumb and forefinger. Then I Righty-Tighty the fitting which rolls the tape onto the threads in the direction of tightening.
I had an email thread with the Marelon tech rep at Forespar and he "assured me" that the buttress threads were far superior for sealing and the Teflon Tape would work great.
They are very small leaks and It would cost me $300 for another haulout to fix them. I should be able to use the little stopper to plug the thru-hull from below while in the water and remove and re-seal but my buddy who dives my boat sometimes tells me that his dry suit is not so dry and did not sound overly excited to get into our water this time of year. I will probably need to wait until spring to do anything about it.
These three thru-hulls cannot move if I back the seacock out because they are mounted in a 3/8" recess designed for the 250 series and then I covered over the top of the mushroom head and the recess with G-flex. (see attachment.) This was the detail that I came up with and ran by the Marelon rep.

 

[Hayden Watson]

Since the valve has not failed, the title is poor.

I would disagree given that they are leaking even though I installed them exactly per their instructions.

 

[Ward H]

jssailem 's posted link is to installation instructions for the Series 93 OEM valves with king nut and does not mention teflon tape.
Hayden Watson 's posted link is to installation instructions for the flange mounting seacocks and does say you can use teflon tape.
Very confusing.

@Hayden Watson In post #8 you talk about buttress threads on your thru hulls.

It was my understanding that only the Series 93 valves used buttress threads. The MF series valves used Standard Straight Mechanic Pipe Threads.

This is based on the following:

Here's an excerpt from a document I have from Forespar talking about Series 93 valve installation that says (note the two sentences I bolded):
“93” SERIES THREAD FORM; The thread form used on these thru-hull fittings and king-nuts is a non-tapered buttress type of thread design. This thread form has a higher load carrying capac-ity, particularly for polymeric materials. Warning, a standard pipe threaded thru-hull fittingwill not fit with the king-nut on these valves. For a standard pipe threaded thru-hull fitting, use our valves that have standard female pipe thread outlets instead of a king-nut base. A buttressthread design with the same amount of clearance as for a conventional pipe thread will give theimpression of greater looseness. However, when the joint is taken up tight, there is a greater areaof surface between threads with the buttress thread form. As with any threaded pipe assembly,Teflon® tape should be applied to the thru-hull threads for a watertight connection.

And in this link, Understanding Thread Forms ,
"Marelon® thru-hulls all have parallel threads. They are “NPT” style threads but are not tapered. No thru-hulls, regardless of material have tapered threads. The technical abbreviation for this parallel thread form is PSM” (American Standard Straight Mechanical Pipe Thread) or, depending on which “expert” you talk to; “NPSC” (American Standard Straight Coupling Pipe Thread)"

I wanted the Series 93 valves with flush fit thru hulls but the packaged Series 93 valves only came with mushroom heads.
Forespar Tech told me I couldn't pair the CF thru hulls with the Series 93 valves because the CF series thru hulls are Standard Straight Mechanic Pipe Threads.
They gave me a part # for the Series 93 valve packaged with the proper threaded, flush fit, thru hulls that I special ordered from Defender.

Talk about confusing.

 

[justsomeguy]

Greater probability of leaking if applied CW.

What?

 

[Hayden Watson]

...
Here's an excerpt from a document I have from Forespar talking about Series 93 valve installation that says (note the two sentences I bolded):
“93” SERIES THREAD FORM; The thread form used on these thru-hull fittings and king-nuts is a non-tapered buttress type of thread design. This thread form has a higher load carrying capacity, particularly for polymeric materials. Warning, a standard pipe threaded thru-hull fitting will not fit with the king-nut on these valves. For a standard pipe threaded thru-hull fitting, use our valves that have standard female pipe thread outlets instead of a king-nut base. A buttress thread design with the same amount of clearance as for a conventional pipe thread will give the impression of greater looseness. However, when the joint is taken up tight, there is a greater area of surface between threads with the buttress thread form. As with any threaded pipe assembly, Teflon® tape should be applied to the thru-hull threads for a watertight connection.
...
I wanted the Series 93 valves with flush fit thru hulls but the packaged Series 93 valves only came with mushroom heads.
Forespar Tech told me I couldn't pair the CF thru hulls with the Series 93 valves because the CF series thru hulls are Standard Straight Mechanic Pipe Threads.
They gave me a part # for the Series 93 valve packaged with the proper threaded, flush fit, thru hulls that I special ordered from Defender.

Talk about confusing.

I was told the same thing on a Friday afternoon by Randal at Forespar. The problem was that I had already been on the hard for a week when he told me that they could make me a series 93 with the King nut threaded with PSM to match my existing through hull the time to make and ship was a big problem. In the end, I got normal series 93 with mushroom head thru-hull and king nut threaded with Buttress. I mounted it in the 3/8" deep by 2½"ø recess and then filled the rest of the recess in the hull and over the mushroom head with G-flex epoxy. As can be seen in the red text above, they say to use Teflon.

 

[Hayden Watson]

What?

It should be wrapped so that it stay wrapped when you thread the parts rather than unwrapping.

 

[dLj]

It should be wrapped so that it stay wrapped when you thread the parts rather than unwrapping.

Correct

What?

CW vs CCW - I guess depends upon how you are looking at the part. If you are looking down onto a male thread, to wrap the tape in the direction of the female thread turning would be CW. If you are looking from the male thread up into the female thread it would then be CCW...

Too bad we don't have a starboard and port type terminology for this one...

dj

 

[dLj]

jssailem 's posted link is to installation instructions for the Series 93 OEM valves with king nut and does not mention teflon tape.
Hayden Watson 's posted link is to installation instructions for the flange mounting seacocks and does say you can use teflon tape.
Very confusing.

Ward,

IMHO for critical pressure tight fittings, I would not use teflon tape no matter what the OEM says - well I guess as long as they don't say you can't use anything else - I've never seen that.... A thru-hull would fall into my definition of this.

Liquid (or paste) sealants would be what I would use. Of course they have to be compatible with the base materials of the joint and the environment the joint is used in...

dj

 

[SEMPERAVANTI41]

I have had lots of problems with Teflon tape & plastic threads. Plasto-Joint Stik Plastic Thread Sealant Stick has solved the problem.

 

[Ralph Johnstone]

Can you supply a little more detail to your drawing of the mushroom exterior of the Marelon thru-hull ? Maybe I'm just blind in one eye and can't see out of the other, but I'm having a little trouble following the construct of this.

 

[Hayden Watson]

This is a Catalina thing. On the Mk2's, they used a recessed thru-hull with a huge head. On the 1/2"ø thru-hull the head is 2.5" across. If you use this thru-hull, you cannot use the seacocks with the buttress threads so you would need to special order one which takes a long time. The recess is formed by a plug that it attached to the form before casting so there is a hump on the inside of the hull. It is more rounded than I show but is still noticeable.

 

[Ward H]

@dLj I agree. I used Sikaflex 291 for my thru hull bedding and also used it on the the thru hull threads.

@Hayden Watson That's a pretty slick solution to the recess to allow a mushroom head thru hull. When I was looking for a solution to allow using a mushroom head th the most frequent response was fill hole and re-drill.

 

[Hayden Watson]

@dLj I agree. I used Sikaflex 291 for my thru hull bedding and also used it on the the thru hull threads.

@Hayden Watson That's a pretty slick solution to the recess to allow a mushroom head thru hull. When I was looking for a solution to allow using a mushroom head the the most frequent response was fill hole and re-drill.

Thanks. To fill the hole requires a 12;1 grind from the bottom of the 3/8" hole so 2*(.375"*12) + 2.5" = about 12"ø repair and that is just the outside and should be 9" on the inside. Too much for this cowboy!