If we are talking bronze fittings consider Loctite 577.

Good info here - for sure wouldn't use thread tape.

forums.ybw.com/index.php?threads/sealing-seacock-to-skin-fitting.452834/

Loctite 572 is recommended see here tech data

www.henkel-adhesives.com/us/en/product/thread-sealants/loctite_572.html

Another link here mentions Loctite 577 as per Ramona but this is a lot faster curing.............

forums.ybw.com/index.php?threads/seacocks-what-sealant-to-use.286447/

Check that the threads of the skin fitting and seacock are compatible - there are straight and tapered threads as per the above links.

I recently used the locktite 577 with ss fittings on the wet exhaust,one elbow was 3/4 of a turn from being tight, I had doubts but turned out good as gold. And as a side benefit it lubes while your doing bits up and avoids galling.

5knotsisbest said..
Thanks all for quick response. Seacock is 316 and the loctite and gasket options looked preferable. I would like to remove in the future without grief. I think both of these would be fine. Cheers.

Loctite 577 takes 72 hours to cure with stainless steel fully but that is for extreme pressures. Cure time varies depending on the metals involved. 577 is not cheap so maybe a visit to Bunnings and check their range.

woko said..
.... on the wet exhaust,one elbow was 3/4 of a turn from being tight.....

That's something I've always wondered but never could get a straight answer to:
When you use a thread locker (or sealant) that ONLY sets when it is exposed to metal, what happens if your fitting is screwed in only loosely, so the metal threads are further apart than if they were fully tightened.
Anyone know with certainty (not speculating) whether those types of thread locker/sealant may never fully set?

I purchased the 577 when doing the job only after searching the like of repco an engineering works and of course the pump shop in Yamba that supplied the ss elbow, union, nipple, tails and the approved hose ( if it sound like a plug it is they have every sort of hose and fitting I have ever needed but no thread sealant ? ) anyway got some 577 from a tractor place, it was an oldish tube and the attendant wasn't sure it was what I needed, so when I got back on board it googled ok so I set to work with it, I let it set for a week and the engine has done 60 hrs since no probs so far. It's not a big green shed sort of product, far more industrial like sugar mills and sewerage plants.
it has defiantly set, that's not speculation

Gotta love spell check

Ramona said..
If we are talking bronze fittings consider Loctite 577.

definetly

Jolene said..
Careful consideration should be taken in sealing 316 threads. I have found that crevice corrosion seems or can be,,very difficult to stop using thread sealants. I have seen fittings that have had their threads eaten away over a very short period of time. Some even have a fissure that start in the thread and then run through the main mass of metal.
The telltale sign is the rust stain running or bubbling on the fitting from a very tiny weep .
This corrosion seems to occur more when the thread sealant is relied upon to fix the fitting in a particular position without preloading the threads. I have fort a loosing battle with one particular 316 fitting on a boat so next time I'm going for a softer compound like Fixtech 15 to seal the thread . What ever you do, if it's 316,,, keep an eye on it!!

I had some special 316 stainless nipples (10mm wall) made up which I welded into the hull of my boat and then fitted S/Steel ball valves to them. Unfortunately I specified 'straight' instead of "tapered" thread to be turned on to the outside of the nipples and had the same issue of getting the handle of the ball valve to stay in a certain position. I tried sealant paste but as it never dries the valve rotated when touched. I ended up using a thick thread tape that enabled me to screw the ball valve on quite firmly to the position I wanted it to stay.

Yes, crevice corrosion is something to be aware of. It relies on the lack of oxygen in an electrolyte (salt water) to have its evil way with your fittings. As long as the fittings are not sitting in stagnate bilge water (where they should be dry) inside your boat or there is no stagnate water trapped in the thread, you should be okay. It also pays to use (have water flow through) your fittings. I only had 4 of these fittings in the boat. Engine intake, deck wash, kitchen in and kitchen sink out. They were all used regularly so no chance of oxygen starved water in them. My shower water was pumped to a cockpit drain above the waterline and the head discharge was above the water line (under the stern) as well. But as Jolene said, keep an eye on them. This goes for any skin fitting as the silicon bronze fittings and valves that were originally used in my hull weren't without their own set of problems. Cheers