Looking at the middle picture the bush looks like a really tight fit on the shaft, Have you tried tapping the bush along the shaft with a hammer? plus maybe a bit of heat? It doesn't look as though the bush has spun in the steel tube , If it had been spinning a lot I think you would have heard a bit of a clatter from it and there would be visible scoring. The reason i mentioned fishing line is that I had some that had wound itself into a rubber, segmented cutless bearing and it took some effort to extract it. If that had been a plain bronze bearing it could possibly have melted inside and that could well have made the thing seize. Well done for getting the thing out, I reckon,( sitting here in the warm and dry and not sitting in a a cold wet dock) that if you can get some movement in the bush you could just be close to fixing the thing.
It happened to me on my little Tosher tug Alacra (we think) now renamed Jo Cox. the bearing had a strange plastic or nylon liner which melted sticking it to the shaft. We didn’t discover it for some time, until it had seriously worn the steel tube. My brilliant engineer bedded the new bearing into place in resin…how he got it exact I do not know. But it saved a lot of cutting and welding. C
Hi Charles - that is a good point - thanks. There was no play in the steel tube intitially - but you are right and will need to test that - or get a new steel tube to fit... yeesh - it just goes on and on.....
You may be able to free the bush/bearing on the shaft with a bit of heat. It is NOT by the way a Cutless bearing, those are the ones with a fluted rubber bearing in a brass collar; you have a plain phosphor bronze bush.
it is rare for the bush to seize onto the shaft. I wonder whether it was a bit tight from the outset, or it could be that the shaft is bent, or the grease supply into the bush may be poor, e.g. no grease grooves in bush.
Once you have the bush free on the shaft you will be able to see whether the shaft has picked up in the bush, but you will not be able to assess the bush until you have stripped the prop off to remove the bush completely, or draw the shaft right out. You will almost certainly need to draw the shaft completely so you might as well get on with that. My hope would be that if the shaft/bush tolerance is indeed tight then you might be able to get a machinist to lightly skim the shaft and bush to remove any damage and then re-use it, but that will depend upon everything else being OK including the shaft being straight. Otherwise it is probably a new shaft and bush, both of which will almost certainly need to be specially made.
Thanks Peter, Richard, Balliol. I managed to get the shaft out with the seized bush - see photo. I'd be interested in any further comments, - I obviously need to get a new bush/cutlass bearing - not sure what other things may be needed - thoughts?
The stern tubes I have seen are a tube threaded at each end. Screwed to each end are the outer cutlas bearing Paul has photoed and on the inside a seal to stop water entering. The prop shaft floats within the seal and the cutlass bearing and if uncoupled from the gearbox coupling can be extracted through the stern tube ( provided the rudder doesn't interfere)
if this can be done the outer cutlas bearing is still attached to the stern tube with the fitting still on the inner hull. It can be unscrewed only after the studs are removed. The studs are there in some part to stop the bearing unwinding when going astern.
being a steel hull the fabrication may be different or ‘custom made ‘ of a different design.
Right, starting to understand a bit better I think, So if you can't free the bronze bush you might have to pull the shaft out backwards with the bush stuck on it which probably means the rudder is in the way or he prop has to come off - neither of which is much fun . It might be possible to pull the shaft out 6 inches or so to get at the back of the bronze piece to get a hammer to it and tap it along the shaft. If that bush has been there for some years and worked OK Ii would imagine that there must be sufficient clearance for the shaft but something has worked its way in.. Hopefully it will be possible to free it, re use all the bits and maybe with a bit of drilling and tapping be on your way again. Good Luck
I might be misinterpreting the problem but to me the bronze part with a gap behind it looks like the end of a 'pusher' and there might be a ring or two of packing inside the assembly, if that is the case then the set screws will need to come out (good luck with that) then it could perhaps be possible to withdraw the shaft with the bronze part seized on it and get at the thing,- might just be some fishing line wound into it.
Paul, if you look at the maucour.fr web site for a flanged bronze stern tube there is a photo of a typical stern tube. The oval shaped fitting is quite large ( and expensive to replace if damaged).
yours may be a bit different as it may have an outer cap to restrain the grease used for lubrication and water seal rather than water anD inner seal.
Not sure if you are saying that the bush (with the shaft) is turning in the outer steel casing or not. If all is seized together I would try soaking in penetrating oil (soak a rag in diesel and wrap it round the lot overnight) and then a dose of heat to try and free the shaft from the bush, then remove the two big studs and try and unscrew the boss from the stern tube.
Paul, as a start I would lock up two nuts on the lower big bolt ( or securely weld a nut on) and try to unscrew it.
if that works it means you need to weld a nut on the upper bolt remain. The heat from welding may help with break the rust stopping bolt from coming out. I am thinking it’s a stud. On a wooden boat it would be a massive wood screw going into the wood with the metal thread changing to metal thread to take a securing nut.
After that follow Balliols suggestion.
I haven't got internal photos - but a couple of other close ups here. The bronze flange has - had - 3 screws. These have sheared off as the bronze is seized to the shaft. The bronze goes through the large steel bush on the outer part - and then to the oval flange. The top screw has to be cut to remove - obviously it, and probably the lower one too - will need replacing. Do this photos stimulate other thoughts?
It can be a bit of a guessing game working out how these things are put together. Have you got an inside photo. This does appear a bit unusual.
I see what appears as a narrow collar right at the back, secured by at least one countersunk slot head set screw. This could be the flanged end of a bronze stern bush, or might just possibly be part of some form of external seal. I think I can see some yellow marks suggesting perhaps a bronze bearing but a scratch around will confirm. Remove any screws.
The larger boss with oval plate attached could be screwed on to the actual stern tube (the bronze tube passing through the stern post from the stuffing gland, but would need that internal photo) and then secured from rotating (and of course secured to the stern post) by the two studs, one of which you have cut off. You really need to try and extract these studs.
Then I would try unscrewing the lot, possibly aided by heat and some judicious radial whacks from a hammer to free off any seized threads.Plenty of penetrating oil or diesel might also help.
I’m only guessing here. Look very closely for further clues. For example old stillson marks can suggest the thread hand. The wrong move could damage things!
Hi Rob, I will stick my head up and suggest the two securing bolts are a set screw and need to be removed then the bearing frame can be unwound as I think the outer is a threaded fitting onto the stern tube.
It’s easy to check if it’s seized by putting the gearbox in neutral and turning the prop.
I think the cutlass bearing could be seized on the prop shaft - the brass or bronze outer and probable 'top hat' are stuck to the shaft. It is impossible to shift this and any attempt seems to pull the shaft. Can anyone advise on how `i might get this off? I will disconnect the shaft from the gearbox tomorrow and hope that gives the ability to pull the shaft from the stern. And - what is best to repair the situation?