Sealing stertube/gland threaded joint

[Poignard]

My boat has a traditional packed inboard bearing/stuffing box that screws onto the front end of the sterntube. What type of sealing compound would readers recommend to seal this threaded joint? Access is very difficult because the threaded end of the sterntube is closely surrounded by a substantial wooden floor. Because of this it will be difficult to do a good cleaning job on the male thread so the compound should be fairly tolerant of some dirt. 3 years ago I used Hemetite Red but this has failed. PTFE tape has been suggested but, because the floor is in the way, it is impossible to wind round the thread.

 

[ccscott49]

There is a paint on sealant, with teflon in it, instead of tape, green in colour, hydraulic guys should have it. Failing that, hylomar might be OK. or even a thinned putty.

 

[Peterduck]

Be very wary about putting anything on a thread which will make it difficult to undo next time, because there will be a next time, and it will probably be you who wants to undo it. I would use simple automotive grease, with a probable preference for water-pump grease. I keep my bronze stern-tube filled with grease via a nipple on a tube leading to the stern-tube. This means that the nipple is easy to reach, so that I can top up the tube easily.
Peter.

 

[ccscott49]

That works fine unless your sterntudes are water fed, to lubricate the outside cutlass. The green teflon stuff is non hardening, so would be ok, it's really for hydraulic fittings, such as aircraft/oilfield, where you are not allowed to use teflon tape. (it can jam small valves and block tiny orifices)

 

[Poignard]

The outboard bearing is water lubricated so that the tube has water aft and grease forward. When the shaft is turning the interface between the water and the grease moves forward as the grease washes out, when the water reaches the threads on the inboard bearing it leaks out around them. Pumping in more grease moves the interface aft again and the leak stops and grease comes out around the threads instead of water. When I leave the boat I give a couple of turns to the greaser and the leak stops completely. The problem is really one of access, because the web-floor supporting the front of the sterntube is in the way of the threaded part so you can`t get at it to clean threads properly. I think I may have to cut away this web-floor, remake the joint properly and then rebuild the web-floor. It`s going to need some hours hanging upside down [this is a deep draught boat], but can`t see any other way. If CCScot can come up with the name of the Teflon sealant, I`d be very grateful.

 

[ccscott49]

Sorry dont know, but try a plumbers or hydraulic place, they use paste type teflon.

 

[l'escargot]

Surely if it is a stuffing box and it is tightened down correctly water won't come past the packing and out round the thread, or am I misunderstanding something from your explanation?

 

[ccscott49]

It shouldn't come out round the thread, but often does!!!

 

[Topcat47]

I use Fernox LSX....available form your friendly neighbourhood plumber's merchant. It fills up the gaps and comes apart/off when you want it to. I use it on my skin fittings as well as my stern tube and all the pipe threads on my hull valves.