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**Dockhead** · 02-05-2018, 04:42

I'm changing a bunch of sea cocks on my boat. Some of them are original to the build, so 17 years old. Others were changed 7 or 8 years.

I changed the previous ones because they were frozen and/or shaft broken -- neglect by the previous owner. But I exercise and lubricate my sea cocks, and always turn them off when I leave the boat overnight, so the rest of them have not suffered from this problem. I've had some external green corrosion but the bronze has otherwise held up just fine. I have tested them in different places and there is no pink.

However, my bilges are damp (keel stepped mast) and the f-ng handles of these ball valves are plated mild steel!

They eventually rust, and the shafts are steel too and rust

. I have bought new bronze ball valves made in Italy with stainless handles and bronze shafts and plated bronze balls.

Here is my question -- is it bad practice to replace the ball valves without replacing the skin fittings?

My skin fittings seem to be absolutely fine -- not the slightest pink color anywhere. I have wire brushed them and checked them everywhere. They have remained well bedded in their places and I don't see any reason to change them.

What say ye?

**GordMay** · 02-05-2018, 04:44

If you see no reason to change them, I doubt I would either.

**Dockhead** · 02-05-2018, 13:08

Thanks, Gord. That's what the local experts are telling me, too.

Another question -- is there a consensus that PTFE sealant AND PTFE tape is the best way to seal the threads?

Mine are all BSP, so there are no NPT/NPF issues.

**a64pilot** · 02-05-2018, 15:55

I’d use dope or tape, never used both for anything.
I’d want it for its properties as a lubricant, to ensure no thread galling. Don’t see as how it would be needed as a sealant, not with almost no pressure ever being on the joint.

terah · 02-05-2018, 15:59

My understanding is that pinking is an issue with brass; the dezincification leaves behind copper which appears pink. So if your through hulls really are bronze (or DZR brass) I'd be tempted to leave them.

Mine unfortunately (and thanks to the barmy RCD requirement of them only needing a service life of 5 years) are brass, so will be replacing the lot.

Had they not been brass I was considering fitting TruDesign ball valves to the existing through hulls.

Only thing is to be very careful not to disturb the seal of the through hull while removing the ball valve.

donradcliffe · 02-05-2018, 16:05

You will be lucky if you can get the valves off without rotating the skin fittings and breaking their seal to the hull. Make sure your new valves and skin fittings are bronze--they sell some crap brass ones in Europe.

As far as sealing the skin fittings (straight thread) to the ball valves goes, I would use tapered thread ball valves, in spite of what the 'experts' may say. The boatyard in Marmaris gave me some super loctite sealant which they swore by--maybe it was their #5776. I went to buy some and it was bloody expensive.

billknny · 02-05-2018, 16:45

Quote:

Originally Posted by donradcliffe

As far as sealing the skin fittings (straight thread) to the ball valves goes, I would use tapered thread ball valves, in spite of what the 'experts' may say. The boatyard in Marmaris gave me some super loctite sealant which they swore by--maybe it was their #5776. I went to buy some and it was bloody expensive.

If you put a wrench on the through hull fitting nut while you turn the ball valve, you shouldn't have a problem with the fitting turning.

I know it is always great fun to disparage experts, but in this case the experts do have good reasons for recommending that you do things the way you should.

The reason that hull fittings and seacocks are made with straight threads instead of tapered ones is physical strength. The hull fittings have straight threads because you want the valve to thread ALL the down and bottom out on the flange.

Threading a tapered thread ball valve onto a straight thread fitting will result is FAR too few of the threads engaging, less than if you used tapered threads on both sides. It will be harder to seal, and with less overlap of the two fittings, significantly weaker mechanically.

Because straight threads do not squash together as tightly as tapered fittings, TFE tape not as good at sealing as the paste pipe dopes.

Holes in your boat are not the place to listen to short-cuts from people telling you the experts are wrong...

Kenomac · 02-05-2018, 17:14

Change them, then you’ll know what they’re made from. Right now... you don’t know for certain.

**a64pilot** · 02-05-2018, 17:33

Good point, assuming both are straight threads then Loctite and not pipe dope or tape ought to be the preferred substance.
Although I doubt there would be any leakage anyway.
Perhaps purple “low strength” or green “wicking” would be best?
Even blue over that size of threads would be tough to remove.

I’d be tempted to put it all together, then apply the green to the assembled joint myself.

**Wotname** · 02-05-2018, 17:54

Surely one wants a thread sealant in this application rather than a thread locking chemistry; of course there is some overlap but the primary function is sealing not locking.

billknny · 02-05-2018, 17:56

Quote:

Originally Posted by Wotname

Surely one wants a thread sealant in this application rather than a thread locking chemistry; of coarse there is some overlap but the primary function is sealing not locking.

Like he ^^^^^ said....

**Wotname** · 02-05-2018, 17:58

As for replacing the skin fittings, my take is these should inspected regularly (as DH is doing) and replaced on condition rather than time in service.

However if one's wallet is deep enough and one is sure that the replacement item is the same as (or better than) the original, then go for it.

malbert73 · 02-05-2018, 19:07

Quote:

Originally Posted by Dockhead

I'm changing a bunch of sea cocks on my boat. Some of them are original to the build, so 17 years old. Others were changed 7 or 8 years.

I changed the previous ones because they were frozen and/or shaft broken -- neglect by the previous owner. But I exercise and lubricate my sea cocks, and always turn them off when I leave the boat overnight, so the rest of them have not suffered from this problem. I've had some external green corrosion but the bronze has otherwise held up just fine. I have tested them in different places and there is no pink.

However, my bilges are damp (keel stepped mast) and the f-ng handles of these ball valves are plated mild steel!

They eventually rust, and the shafts are steel too and rust

. I have bought new bronze ball valves made in Italy with stainless handles and bronze shafts and plated bronze balls.

Here is my question -- is it bad practice to replace the ball valves without replacing the skin fittings?

My skin fittings seem to be absolutely fine -- not the slightest pink color anywhere. I have wire brushed them and checked them everywhere. They have remained well bedded in their places and I don't see any reason to change them.

What say ye?

Just out of curiosity how do you lubricate them and what do you use?