Stern tube leak

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  • 18th August 2010 at 12:28 pm #11113

      We are experiencing a small leak from around the stern tube, where it passes into the hull. Nothing visible from the outside, and it's been suggested that it may come from where the tube screws into the cutless bearing. Anyone know how these things were put in?

      2nd September 2010 at 10:56 am #11900

        Hi Lionel,

        The stern tube itself, copper or plastic, is moulded into the boat usually during the build process. This could be leaking as water can wick along the tube without it being visually obvious. You could rebond the edge of the tube that you can see on the outside. The cutlass bearing slides into the tube and is usually held by grub screws. As water flows freely around the propshaft a water tight seal here is not required, it would be sealed off by the stuffing box or rubber seal assembly inboard. You need to make sure this end of the tube is not the cause of your problem before rebonding the stern tube. Geoff Linter Commodore, HT asso.

        2nd September 2010 at 4:28 pm #11901

          Geoff,

          thanks for this. A boat builder at Ramsgate where we hauled out suggested that the tube (looks like bronze) is threaded into the back of the exterior casting, which holds the cutless bearing. He thought that vibration, or even catalytic corrosion loosened the thread, allowing water to wick around the thread and thence up alongside the shaft. It's definitely coming in from around where the shaft passes thru the deadwood, about 10mm depth per hour. We are lifting out next week and I'm proposing to extract the tube and re-bed as a proper solution. If the thread's secure and the exterior casting safely bedded with sealant this should do it?

          6th September 2010 at 2:36 pm #11902

            I agree with you Lionel. That should do it. Excuse my mistake in calling the Bronze part Copper. I realised after I had sent the reply…Senior moment…Geoff

            8th September 2010 at 6:06 pm #11903

              Geoff,

              thanks for your help and support. Everything is out now, the tube is luckily not damaged and I'm cleaning it all up. The problem would appear to have been the lower bolt which holds on the cutless bearing. These bolts had just been bedded in on sealing putty, with a slot on the outside end to hold the bolt tight with a screwdriver. Vibration had caused the lower bolt to loosen and allow water to seep in. We've re-bedded the bolts and glassed over the heads inside to seal the inboard end, then we'll re-bed the cutless bearing on new flexible sealer, before screwing in the tube with PTFE tape and more flexible sealer. Hopefully this should do it (fingers crossed.) The inner flexible bearing with greaser is OK.
              Regards,

              Lionel

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