Stern Tube removal on Birchwood 340AC (2001)

[JMcKillop]

Hopefully someone can advise as how I should proceed to repairing a leak which appears to be coming from the stern tube bearing housing bottom bolt/flange . The marina last year just put some Sikaflex around the outer side as can be seen from the attached pics. (It looks like it has been welded, but it's not). It did the trick for a short time but the leak has reappeared.
Is the flange screwed onto the stern tube? If it is, then any sealant would be displaced when screwing back in place. Question 1; which sealant/adhesive should I use? Question 2; What method should I adopt to carry out the disassembly reassembly of the flange/tube. I have attached some pics. Any advice would be much appreciated. If anyone needs more info, please ask.
Regards

 

[Tranona]

The outer bearing housing may be screwed onto the tube and locked into place with coach screws into the GRP or bolted through the GRP with nuts on the inside in much the same way as the inboard housing is bolted through in the other 2 photos. Can you see down the inside of the skeg to see if there are any nuts?

Water can obviously get in there if the sealant fails. Normally a non setting sealant such as a polysulphide or butyl would be appropriate rather than an adhesive sealant like Sika as the latter makes it a pig to take apart, for example if you need to change the cutless bearing.

 

[JMcKillop]

Thanks @Tranona for reply . Yes, it is bolted through the GRP as can be seen from pic 4 from the inside. Obviously the bottom nut is going to be a real challenge to access. If screwed onto the tube, my issue will be as to how to disassemble and reassemble without the sealant being displaced.

 

[oldgit]

Is engine movement ie the engine flexible mounts have lost their integrity, the shaft then inducing that stern tube to move and causing the sealant to fail. ?

 

[JMcKillop]

Is engine movement ie the engine flexible mounts have lost their integrity, the shaft then inducing that stern tube to move and causing the sealant to fail. ?

Thanks for reply @oldgit . The engine mounting are intact. Any engine movement, IMHO would be suppressed by the inboard packing gland housing. I believe that movement perhaps may have been as a result of years of inland water cruising and tipping the prop a few times. My dilemma is how to carry out the repair.

 

[Tranona]

I suspect the bearing housing is screwed onto the tube and when it is on fully the bolt holes line up to lock it into place. It could however be that there is a flange on the tube inside the boat and the bearing housing just slides on the tube and clamped by the two bolts.

 

[JMcKillop]

I suspect the bearing housing is screwed onto the tube and when it is on fully the bolt holes line up to lock it into place. It could however be that there is a flange on the tube inside the boat and the bearing housing just slides on the tube and clamped by the two bolts.

From my pic, I don't believe that there is a flange inside the boat.. I have borrowed a friends endoscope and will have a closer inspection tomorrow and revert back. Which polysulphide would up recommend?

 

[Tranona]

If the nuts do just bear on the GRP this could be the cause as it is difficult to consolidate the laminate down there and the nut may not be tight. Arbokol 100 is the sealant I use.

 

[Tzu]

On my Westerly... the tube screws into the cutless bearing housing. When I removed the housing the end of the tube came with it, I am thus now needing to replace the tube. I believe my stern tube was cracked at the join area and this failed when removing the housing so dont be surprised if the job gets bigger than you hoped. (my broken stern tube is still in the boat which I've not been allowed near for 3 months since this lockdown started.

nb.. the bearing housing on mine was nut and bolted, a long 3/8 drive extension and socket enabled me to get to it for removal but I will need to strip some engine parts to enable me to get in and have enough room for re-assembly (I dont work particularly well upside down for extended periods)

Purely my observations, I hope it goes well for you

 

[Malish]

On both my Rivals the cutless bearing holder (similar design by Stuart Turner) screwed onto the end of the stern tube and the two locking screws just screwed into the fibreglass of the hull. Their screw holes were not blind but passed into the interior of the boat (and the thread on the fibreglass was worn). My first attempt to replace a cutless bearing required a second haul out due to water ingress through the locking screw fittings which showed up as water coming in below the stuffing box. I remade the threads in the fibreglass with epoxy filler and re-cut them before applying mastic (of some form) when reattaching the cutless holder. Dry as a bone ever since.

 

[JMcKillop]

I suspect the bearing housing is screwed onto the tube and when it is on fully the bolt holes line up to lock it into place. It could however be that there is a flange on the tube inside the boat and the bearing housing just slides on the tube and clamped by the two bolts. If the nuts do just bear on the GRP this could be the cause as it is difficult to consolidate the laminate down there and the nut may not be tight. Arbokol 100 is the sealant I use.

Thanks to all posters who took the time to reply . I took a couple of detail pics today and can confirm that the bearing housing is screwed into the tube , also the stuffing gland assembly on the inboard bulkhead.
There is no flange on the inside, bolts appear to be tightened against the GRP. See pics. Looks like the complete stern tube assembly has to come out