Stern Tube leaking

[CAPTAIN FANTASTIC]

The stern tube is leaking. The boat is a Macwester Wight with a Volvo MD11C and 1 inch shaft. The leak is where the tube joins the stern inside; I have pumped it with grease but makes no difference. Anyone knows how the stern tube is connected to the stern and possible repairs?

 

[ghostlymoron]

The stern tube is usually threaded at both ends. The outboard end screws over the holder for the cutlass bearing which is screwed to the dead wood. For more details see cox engineering website. It's difficult to see how it could become detached, maybe it's worn or corroded.

 

[Tranona]

Difficult to say without knowing what type it is. The common cause of leaks at the aft end is because the tube has become detached from the GRP. From memory think you have a screw on bearing housing locked in place with two set screws. You need to remove this to find out where the water is getting in. Grease will not do anything. It is there to lubricate the packing, not stop water getting in.

 

[ghostlymoron]

After checking Vyv's website, I can't find any details about stern tubes. I'll try googling - you could do the same! I think there's some pictures in my book on simple boat maintenance.

 

[vyv_cox]

After checking Vyv's website, I can't find any details about stern tubes. I'll try googling - you could do the same! I think there's some pictures in my book on simple boat maintenance.

Yes that's true. If anyone has any photos or info I will be pleased to add them. Most of the ones I have come across are a simple tube glassed into the boat. The one on Cecilia, dating from 1972, seems to be the same but with a flange at the forward end and a screwed bearing holder aft.

 

[superheat6k]

This happened on my last boat on its maiden voyage from Chertsey on the Thames, back to Gosport. Some prop damage caused excessive vibration which caused one of the two bolts securing the shaft log in place through the deadwood to shear, allowing the water to dribble in. Had it been the lower bolt then this was completely out of sight, so the boat would have filled with water, fortunately after I observed the auto bilge pump cutting in, I noticed the upper bolt drifting inwards before it popped out of its hole.

I have an ignorant Marina Manager at a certain Thames marina to thank for this, but that's another story !

The fix was to completely remove the shaft and then the shaft log, clean and re-seal with Sikaflex 291. I also drilled the bolts out from M10 to M12. The process was very fiddly, especially locating the lower obscured bolt.

 

[ghostlymoron]

This is a shot of a typical stern bearing http://s496.photobucket.com/user/ghostlymoron/media/Anemone/anemoneprop.jpg.html?sort=3&o=3 it had just been taken off and re-bedded. Does anyone know if the hex heads shown are attached to pointed screws or parallel screws?

 

[alahol2]

The stern tube is usually threaded at both ends. The outboard end screws over the holder for the cutlass bearing which is screwed to the dead wood. For more details see cox engineering website. It's difficult to see how it could become detached, maybe it's worn or corroded.

Yes, except that my stern tube is threaded on the outside and it screws into the bearing holder. The bearing holder is bolted onto the deadwood. Probably worth stating that this is a bronze sterntube. I assume a GRP tube would be glassed in to the deadwood.

 

[CAPTAIN FANTASTIC]

This happened on my last boat on its maiden voyage from Chertsey on the Thames, back to Gosport. Some prop damage caused excessive vibration which caused one of the two bolts securing the shaft log in place through the deadwood to shear, allowing the water to dribble in. Had it been the lower bolt then this was completely out of sight, so the boat would have filled with water, fortunately after I observed the auto bilge pump cutting in, I noticed the upper bolt drifting inwards before it popped out of its hole.

I have an ignorant Marina Manager at a certain Thames marina to thank for this, but that's another story !

The fix was to completely remove the shaft and then the shaft log, clean and re-seal with Sikaflex 291. I also drilled the bolts out from M10 to M12. The process was very fiddly, especially locating the lower obscured bolt.

Thanks to all for the replies. One of my engine rubber mounts got damaged and I had to replace it last year; the engine was realigned after the new mount was fitted but it appears that the vibration damaged the stern tube and has been leaking ever since. I would have to remove the stern tube and re-seal it.

 

[CAPTAIN FANTASTIC]

Yes that's true. If anyone has any photos or info I will be pleased to add them. Most of the ones I have come across are a simple tube glassed into the boat. The one on Cecilia, dating from 1972, seems to be the same but with a flange at the forward end and a screwed bearing holder aft.

Thank you for the reply. If I do the job myself (finding the time to do it myself is difficult), I will take pictures and I will post them here.

 

[alahol2]

Here are the photos from when I replaced the white metal stern bearing with a composite one.

Just a pair of washers and nuts hold the bolts through the bearing carrier. Wires are from the hull anode. Needed nearly 3ft of socket extensions to be able to get under the stern tube and turn the nut off the lower bolt.

After unscrewing the bearing carrier. The stern tube can be seen extending flush with the deadwood.

The bearing carrier with the white metal bearing.

The bearing carrier with the white metal having been machined out and the new composite bearing ready to be epoxied in place.

The bearing carrier needs a shaped backing pad to keep it square to the shaft.

Refitted with the bearing epoxied in and left slightly proud to ease removal next time, the epoxy can be softened with heat. The shaped backing pad was a sliver of teak painted with epoxy primer. Thread and everything else bedded on CT1 mastic. Same rigmarole with socket extensions to tighten the lower nut.

It's all still fine after 4 seasons.

Should have said if Vyv wants to use any of the photos, feel free.

 

[NickRobinson]

My Macwester had the smaller Stuart stern gear and it was the inner flange that came loose and leaked. Screwed onto the tube, the stuffing box was secured by two flimsy looking wood screws.

It sounds like you won't have any option but to remove the outer coach(?) bolts from the deadwood and unscrew the Cutless housing to reseal BUT Macwester Owners Club warn that it's difficult to re-screw into the deadwood; perhaps due to insufficient material.
hope it goes OK-
N

Just seen Alahol's post after writing mine.- very comprehensive. The MOA advice may only refer to the 26's N

 

[CAPTAIN FANTASTIC]

Thanks NickRobinson, sounds like a very fiddly job.

 

[CAPTAIN FANTASTIC]

Great pictures alahol2 and very usuful

 

[ripvan1]

On my Mac 26 I thought the leak was coming from the bottom bolt on the inner flange so proceeded to dismantle the lot. When it came to undoing the prop tube (bronze/brass) the threads crumbled when it came out. This was obviously where the the drip started and wonder whether electrolysis had caused this (40 year old boat on drying mooring?) Had a new tube made up and touch wood OK to date.
If leak on OP's boat is from the lower flange bolt which is beneath the tube then shaft needs to be pulled and tube needs to come out to gain access to bolt. (and even then it's a fiddly job) good luck

 

[CAPTAIN FANTASTIC]

On my Mac 26 I thought the leak was coming from the bottom bolt on the inner flange so proceeded to dismantle the lot. When it came to undoing the prop tube (bronze/brass) the threads crumbled when it came out. This was obviously where the the drip started and wonder whether electrolysis had caused this (40 year old boat on drying mooring?) Had a new tube made up and touch wood OK to date.
If leak on OP's boat is from the lower flange bolt which is beneath the tube then shaft needs to be pulled and tube needs to come out to gain access to bolt. (and even then it's a fiddly job) good luck

Yes, the leak is from inside lower flange, so it is very likely that the tube may need replacement. Thank you for the information. I may be looking for a marine mechanic, near Southampton, to do the job for me.

 

[vyv_cox]

Here are the photos from when I replaced the white metal stern bearing with a composite one.

.............

It's all still fine after 4 seasons.

Should have said if Vyv wants to use any of the photos, feel free.

Thanks very much, I will use them. Your arrangement is almost identical to mine on Cecilia, except that my tube protrudes further. I also used a Maritex bearing but it is epoxied into the fixed part of the tube. The old white metal bearing had a larger OD at the outboard end, the screwed cap holding it in place. I have cut the short, larger OD piece off and retained it to butt up to the Maritex bearing.

 

[noboatforoldmen]

I have macwester atlanta, same problem, took the whole lot to bits to discover that the stern gland was only screwed hand tight onto shaft with no thread sealer. Buckets of water and grease in bilges - whole lot out, engine, fuel tank, shaft, all about to be reassembled with hemp and waterproof sealer.

 

[noboatforoldmen]

p.s. the stern tube on ours exits through hole in skeg and is screwed on to cutlass bearing housing with water inlets. The problem is where it meets dead wood at the engine end, loose stern gland (stuffing box) on mine.