Seized prop shafts on 1961 62ft Feadship TIKY

we are on the way to finishing the refit on my 1961 62ft Feadship TIKY but we have a problem with the sterntube aft bearings, both of which seized up solid on the shafts after running the boat in the river for a few minutes at slow revs, the first time since she was relaunched. As Im sure you can imagine this is very disappointing

The tubes are grease filled with a bronze stuffing box and packing at the fwd inboard end of the tube and a gland at the aft end of the tube and a cutlass bearing within an A bracket at the prop. These aft bearings were replaced in mild steel by The Yard as part of the realignment work done last year, apparently made exactly as per the original bearings except that the original bearings were cast iron of some sort and the replacements were fabricated from mild steel. She had new s/s shafts fitted by me in Spain when we fitted the rebuilt Gardners and new Python CV drives. The boat returned home from Mallorca under her own power with the old bearings and the new shafts, apparently without problems but when the alignment work to the stern gear was being done at Foxs we discovered the flange of one of the original bearing had cracked. The yard tried to weld the cracked flange but were unable to ( presumably because they were cast) , so two new aft bearings were fabricated in mild steel with a spiral and lipseal etc , supposedly identical to the originals that were removed.

I can only assume the shafts seized as a result of a combination of incorrect tolerances being provided between shaft and aft bearing and not enough lubrication (although perhaps the original cast bearings were of some type of sphinctered graphite material, possibly more suitable for use as bearings with mild steel shafts). In any event both bearings were so badly seized they had to be cut away from the shafts and it was apparent the shafts had picked up some of the bearing material which became welded to them

The yard are not sure what was the tolerance was on the replacement bearings or indeed if anyone had turned the greasers before running the engines. although there appeared to be grease in the bearings when I looked at them last Friday .

The shafts can apparently have this material polished off, which is good news, so we now need to decide what to do about the bearings. Of course , it would be nice to replace the entire shaft /tube arrangement with a more modern water cooled system but I am advised this would be a lengthy and expensive job and in any event beyond the capabilities of the local yards, so we have to find some other cost effective solution.

I am now advised that having steel bearings and steel shafts is not a great combination so the yard are now proposing to remake the bearings more/less as before but with a sleeve fitted, probably made out of some form of bronze, with of course the appropriate tolerance ( NB the bearing isn't strict speaking a bearing as most of the load is taken by the cutlass in the A bracket), and a seal at the aft end of the steel bearing to keep the grease in but still allow some through to lubricate the bearings when pressure applied from the greasers

Does anyone have any experience of grease filled tubes and any advice to offer about what material the sleeve should be, tolerance we should provide and the best type of seal to use ?

regards
David