Tricky Shaft Log Leak Repair - SailNet Community

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  #1  
Old 04-15-2009
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Tricky Shaft Log Leak Repair

I'm working on a fix for leaks in a Mull 34 named Soma, and I want to ask the Sailnet community whether you have any ideas. We have finally figured out where it leaks, and now the trouble is how to fix it.

The boat has a sump in the bilge, a hollow area in the keel, with a hydraulic drive motor in it. The propeller shaft exits the boat through a shaft log at the aft end of the sump, and then passes through approximately 2 feet of fiberglass before it exits at the trailing edge of the fin keel. The leak originates inside of this tunnel through the keel. We confirmed this by pressurizing it with a shop vac and some soapy water. The air bubbled up out of many surprising locations in the bilge of the boat.

With the launch date set for May 2nd, what can we do to fix the leaks before then? The ideas put forth so far are filling the tube/tunnel with epoxy and drilling a new hole (how to keep a 1 1/2" drill bit on course for 2 feet?), boring the hole bigger to put in a fiberglass tube (ditto?), coating the inside with gelcoat (how?), or try penetrating epoxy (how do we know we got all the leaks?)

The sure-fire fix would be to rip the side of the keel open, and rebuild the tube, but the launch date is coming fast. Has anybody here faced a problem like this before?
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Old 04-15-2009
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Geez, that sounds expensive. I'm still not quite sure how you determined there is a leak. Seems like that tunnel should have water in it and there should be some sort of a stuffing box in the bilge to keep the water in the tunnel from coming in the boat. I have a similar arrangement in my boat. The PSS shaft seal is inside the boat bilge. What do you have for a stuffing box?


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Last edited by erps; 04-15-2009 at 09:18 PM.
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Spray the interior of the tube with this stuff...
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Old 04-16-2009
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If the boat is on stands, a person could also run water in the bilge and see if it leaks out.
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Old 04-16-2009
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Hey, thanks for the replies! I always know that there's something I'm assuming, but not communicating in a message. Yes, here in the frozen North, the sailing club has to keep the boat on its trailer for half the year. We know that water from inside the hull leaks out through the propeller shaft tube, because it formed a rusty, frozen stream out of the gland and down the side of the keel!

The boat has a PSS dripless shaft seal, but it hasn't been too useful in this case, as it would fill up with water from the leak-- about 20-25 gallons per day last season! With the propeller shaft and the PSS shaft seal removed, we clamped a piece of rubber over the inboard side of the shaft log, and stuck the blower hose from the shop vac in the gland from the outside. With the tube thus pressurized, air leaked into the boat from various spots in the bilge, including one of the forward keel bolts. (The source of the rust?) I'm pretty certain that the water enters a crack inside the tube, and runs along the encapsulated lead ballast to the keel bolt-- we found a lot of the same wicking when we tore most of the (saturated) polyester fairing compound off the keel a few years ago, to replace it with epoxy compound.

I will give the Captain Tolley's a try. I hadn't thought of spraying it in. (At $14.99 for two ounces, it's mighty expensive to try to pour it in!) Thanks for the suggestion!
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In theory, if the cracks aren't too large, it should fill them and seal them. Good luck.
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Originally Posted by JonG View Post
Hey, thanks for the replies! I always know that there's something I'm assuming, but not communicating in a message. Yes, here in the frozen North, the sailing club has to keep the boat on its trailer for half the year. We know that water from inside the hull leaks out through the propeller shaft tube, because it formed a rusty, frozen stream out of the gland and down the side of the keel!

The boat has a PSS dripless shaft seal, but it hasn't been too useful in this case, as it would fill up with water from the leak-- about 20-25 gallons per day last season! With the propeller shaft and the PSS shaft seal removed, we clamped a piece of rubber over the inboard side of the shaft log, and stuck the blower hose from the shop vac in the gland from the outside. With the tube thus pressurized, air leaked into the boat from various spots in the bilge, including one of the forward keel bolts. (The source of the rust?) I'm pretty certain that the water enters a crack inside the tube, and runs along the encapsulated lead ballast to the keel bolt-- we found a lot of the same wicking when we tore most of the (saturated) polyester fairing compound off the keel a few years ago, to replace it with epoxy compound.

I will give the Captain Tolley's a try. I hadn't thought of spraying it in. (At $14.99 for two ounces, it's mighty expensive to try to pour it in!) Thanks for the suggestion!
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 04-27-2009
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Exclamation

I think I have a very similar if not identical problem. Boat just went in a few weeks ago and just this past weekend as I was playing around with the stuffing box I noticed a small leak coming from the platform the muffler is screwed onto. It only leaks when the engine is in gear and at cruising RPM and it sprays a very small amount of water from a small pin sized hole. The muffler seems to sit on a raised platform of fiberglass ontop the solid fiberglass of the hull so that the screws don't screw into the hole. It is inbetween these two layers that I notice the leak. At first I thought it might be the muffler but I took it out and it is dry. Also it does not leak at all unless this boat is cranking under power so I think it could be the shaft log leaking.

Also as you can see from the 2nd pic, the boat does not have an external shaft strut - the shaft just comes right out of them hull.

Is this something that is a major problem? Should the boat be hauled or is this something that can wait till end of season? Is this type of thing normal?

[IMG]Photobucket[/IMG]

[IMG]Photobucket[/IMG]
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Old 04-27-2009
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Also what is surrounding the shaft log? I mean in the area from where the shaft log starts at the rear near the prop to it emerges inside the boat by the stuffing box. What is surrounding it inside the boat in the area that you can't see? Is it hollow? Is it solid fiber glass? Is it coreing material? I am just wondering because if there is a small leak in the shaft log but is a very small one that can wait until next haul - I want to know if the water getting in on the outside of the shaft log is damaging anything else?
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