Antares 760 stern tube delaminating

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spray

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My stern tube is delaminating, I cannot find another similar boat ashore to compare.
I was going to wrap some glass cloth and resin but does this tube have a protective cover? Quite amazing that the recent survey made no mention of it. There is also a socket head cap screw one side but the other side is just blank, I wondered if this was the lubricating raw water exit. Your advice would be appreciated.
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There are two screws originally to secure shaft bearing. You should laminate really well and cover with epoxy, primer and AF.
 
spray said:
My stern tube is delaminating, I cannot find another similar boat ashore to compare.
I was going to wrap some glass cloth and resin but does this tube have a protective cover? Quite amazing that the recent survey made no mention of it. There is also a socket head cap screw one side but the other side is just blank, I wondered if this was the lubricating raw water exit. Your advice would be appreciated.
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Difficult to diagnose from one picture and no history but I believe that is abrasion, not delamination. Looks like something got wrapped around the prop and the tube, so that the wrap got dragged around the tube by the rotating prop causing the abrasion. Inspect carefully to see if the tube has rotated in the hull/skeg, check the water injection hose, inside the boat, is still pointing upwards (see edit below). Measure the outside diameter of the section of the tube inside the boat (mine is 60mm) and compare that with the outside diameter if the abraded section so you know how much material has been lost. Remove the shaft and cutlass bearing so you can make good the two bearing locating screws. If the tube has not rotated at all then maybe just wrap in glass rovings and epoxy resin. Put in a new bearing while you are at it, and new locating screws. There is no water exit hole, there should be two screws. Mine look like they are plastic/nylon. this is mine......

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Edit: Just checked the position of my water injection hose and it is not at the top so that may not be a good indicator that the tube has rotated:-

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Plum said:
Difficult to diagnose from one picture and no history but I believe that is abrasion, not delamination. Looks like something got wrapped around the prop and the tube, so that the wrap got dragged around the tube by the rotating prop causing the abrasion. Inspect carefully to see if the tube has rotated in the hull/skeg, check the water injection hose, inside the boat, is still pointing upwards (see edit below). Measure the outside diameter of the section of the tube inside the boat (mine is 60mm) and compare that with the outside diameter if the abraded section so you know how much material has been lost. Remove the shaft and cutlass bearing so you can make good the two bearing locating screws. If the tube has not rotated at all then maybe just wrap in glass rovings and epoxy resin. Put in a new bearing while you are at it, and new locating screws. There is no water exit hole, there should be two screws. Mine look like they are plastic/nylon. this is mine......

View attachment 190560


Edit: Just checked the position of my water injection hose and it is not at the top so that may not be a good indicator that the tube has rotated:-

View attachment 190561
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Plum, thank you very much for your detailed reply. I am pretty sure the bearing has not rotated and I don’t think much material has been lost, but I will check everything you mentioned. Your thoughts of something dragging round by the prop is probably spot on.
I am not sure this is relevant so the excuse thread drift but do your prop anodes wear out after about 5 months?
 
spray said:
Plum, thank you very much for your detailed reply. I am pretty sure the bearing has not rotated and I don’t think much material has been lost, but I will check everything you mentioned. Your thoughts of something dragging round by the prop is probably spot on.
I am not sure this is relevant so the excuse thread drift but do your prop anodes wear out after about 5 months?
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My prop anode wears out in 4 months! However, I also have a hull mounted anode with good electrical connection (low resistance) to the prop to provide protection when the prop anode has gone. Appears to work as prop is 25 years old 😀
 
Plum, thanks again, much appreciated. 4 months is a very short life for an anode, I’ll check mine for resistance. I measured my external tube diameter, 66mm, I don’t think much material has been lost on a closer inspection. I haven’t been able to measure the internal tube diameter yet. I’m certain that the tube has not rotated. The two bolts must be nylon as you say and care is needed that they don’t foul the propshaft. I will wrap a few layers of fibreglass tape and epoxy resin and keep a close eye on it.
 
spray said:
Plum, thanks again, much appreciated. 4 months is a very short life for an anode, I’ll check mine for resistance. I measured my external tube diameter, 66mm, I don’t think much material has been lost on a closer inspection. I haven’t been able to measure the internal tube diameter yet. I’m certain that the tube has not rotated. The two bolts must be nylon as you say and care is needed that they don’t foul the propshaft. I will wrap a few layers of fibreglass tape and epoxy resin and keep a close eye on it.
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Yes, the prop anode is very small for the size of prop but my hull mounted anode will last 1 & 1/2 years
 
Plum said:
Yes, the prop anode is very small for the size of prop but my hull mounted anode will last 1 & 1/2 years
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I have a large pear shaped anode on the forward end of the skeg but I will add another nearer the prop as you have done. It’s a pity that there are no divers or scrubbing posts near my marina to make regular anode checks.
 
spray said:
I have a large pear shaped anode on the forward end of the skeg but I will add another nearer the prop as you have done. It’s a pity that there are no divers or scrubbing posts near my marina to make regular anode checks.
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I am lucky in that here at Bridgemarsh Marina on the River Crouch there are scrubbing posts that are free to use for berth holders.
 
spray said:
I have a large pear shaped anode on the forward end of the skeg but I will add another nearer the prop as you have done. It’s a pity that there are no divers or scrubbing posts near my marina to make regular anode checks.
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The one on the skeg is probably not doing anything. The hull anode must be bonded to the prop shaft to protect the prop. Usually this is done by wiring to the gearbox housing. Painting the prop to reduce the exposed surface area also helps.
 
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