Stern tube reassembly ... ?

[Zen Zero]

We plan to reassemble Nereide's stern tube, and drive shaft at the weekend. They came apart to address a leak that developed during 14 months ashore for extensive refitting. Guess how we found the leak?

Would anyone like to suggest the correct order for putting things back together?

I'm guessing it should all be dry fitted, with new stuffing in the stuffing box, drive shaft connected to gearbox etc before smearing sealant, screwing down and hoping not to have to pay for another lift out/in.

All suggestions gratefully considered.

Thanks

 

[Burnham Bob]

sounds silly but it depends on your stern tube. my old one was threaded at both ends and screwed onto a boss at the transom and then the stuffing box screwed onto the other end.

needless to say, if you tightened the tube onto the boss, the stuffing box ended up when tight at a bit of an angle but there was enough thread to form a seal if you squared the stuffing box up to where it could be secured to a cross member and then glassed in. the guy who bought that boat off me saw a slight leak at the stuffing box and rather than turn the greaser or tighten the stuffing box, rotated the tube to close the gap. that losseded the seal at the transom and he got a much bigger leak at the other end.

as long as you've got enough turns of packing and tighten the stuffing box (never found a perfect answer to how tight it should be but i always tightened until i could feel the propshaft being restricted a little when turned by hand - seemed to work!) you should be okay but i always used to turn the greaser as much as i could even though i know a lot of grease went out into the water.

quick tip from an engineer about how hot a stuffing box should get was that something you can keep your hand on is not hot - its just warm. again worked for me.

whatever your stern tube type and formation, none of this is rovket science - in fact its quite crude unless you've got one of the posh patent efforts.

just work out how its supposed to work and that will tell you how to assemble it.

 

[Zen Zero]

Thanks for your advice Bob. Nereide's stern tube is a bronze casting, consisting of a wide oblong flange from which a cylindrical section rises and culminates in the stuffing box. I ought to point out that Nereide is a wooden boat. The flange mates with the wooden keel piece and straddles the hole through which the prop shaft passes. It's really quite a pleasing piece of boat, aesthetically speaking; I'd love to polish it and keep it shiny, but my co-owner is fed-up enough with the time (and expense) this refit is taking.

So the steps to relaunch are:
1. dry-out until the wooden structure is bone dry
2. epoxy it (paint exposed wood with thinned epoxy resin)
3. dry assemble prop shaft, stuffing box and stern-tube
4. sikaflex the flange
5. screw it down
6. put the rudder back on
7. lift-in
8. check for leaks
9 repeat as required

 

[Tranona]

You seem to be just describing the inboard housing. Presumably the stern tube itself and the aft cutless bearing housing are still in place. Normally the inboard housing is screwed onto the tube, bedded in sealer (I use a Polysulphide) and then locked into place with two screws or coach bolts screwed into the wood. The housing does not have to go hard down on the thread as the sealer makes the seal.