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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #21  
Old 04-29-2009
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Originally Posted by sailingdog View Post
water can run uphill, via capillary action. That's how trees get water from their roots... and it can go a long, long way uphill.
I don't think this is a question of water running "uphill" anyway, since the entire platform that the muffler rests on is below the waterline.

NK, I'm very curious too. Our boat is virtually identical to yours, i.e. same rudder/skeg/aperture, exact same platform over the stuffing box, etc (but our waterlift muffler is mounted elsewhere).

I have always assumed that the area under the platform was filled with chop and resin, and that the shaft tube ran through this "solid" area. But practically speaking, I'm not certain that it could be completely solid. There could easily be some small hairline voids through which water under pressure could pass. The source would most likely be a bad seal where the shaft tube exits the boat in the aperture, with vibration/cavitation from the spinning prop exacerbating it and allowing some ingress.

Normally I would advise haul the boat and sort it out. But if I was in your shoes, having had some budget busting repairs already this season, I would probably hold off until next winter haul-out. (This assumes you are not planning another long voyage this year?) Keep a close eye on it, maybe see if you can stop the leak by sealing the pinhole. You might also try diving and sealing around the shaft tube with a sealant that can cure underwater.

Good luck!
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Last edited by JohnRPollard; 04-29-2009 at 06:43 PM. Reason: typos
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  #22  
Old 04-29-2009
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Quote:
Originally Posted by nk235 View Post
Also what is surrounding the shaft log? Meaning in the part of the boat you can't see from the prop to where it enters the cabin near the stuffing box? Is it hollow? is it fiberglass? I'm trying to figure out that if water is getting outside the shaft log, what it might be damaging
That shaft log could be going through solid fiberglass, or the builder may have filled the void with some other material such as ballast, foam, or something else. Without knowing what the builder did, I can only make an educated guess, and I would have to agree with another poster that they probably used a fiberglass tube as the shaft log, and probably not through solid glass (too expensive). If that is indeed the case, then inboard end of that tube has to meet the fabric layers of the hull where the stuffing box is mounted. That's a somewhat awkward joint to make with fiberglass.

Since the leak only occurs when you have the boat under way, clearly the flexing of the hull from the force of the propeller pushing on it opens up the leak path, and cutting power pinches it off. It's far enough below the water line that hydrostatic pressure will cause the leak to spray, as you have observed.

Putting it together, here's a guess: There's a crack at the inboard end of the fiberglass tube/shaft log that opens up when the hull flexes under power.

If it were my boat, I'd keep an eye on it through out this season, and then address it after haul-out in the fall.
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  #23  
Old 04-29-2009
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John - Yes I can say by just the picture of your boat in your signature it looks exactly like mine. I am thinking along the same lines as you right now by trying to seal the leak in the boat and then once the water warms up a bit diving under and applying something on the underside. I am curious and tempted to try drilling a small hole into that platform that the muffler is screwed onto just to see what happens - if it is solid or hollow and if water comes out. What do you think? Dumb idea?
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Old 04-29-2009
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Quote:
I am curious and tempted to try drilling a small hole into that platform that the muffler is screwed onto just to see what happens - if it is solid or hollow and if water comes out. What do you think? Dumb idea?
That would yield some valuable information. I'm guessing it would yield some increase in your heart rate while the hole is being drilled though. You'll need a plan to stop the leak if you strike a gusher.
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Old 04-29-2009
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That would yield some valuable information. I'm guessing it would yield some increase in your heart rate while the hole is being drilled though. You'll need a plan to stop the leak if you strike a gusher.
Yes I will be prepared to stop the leak but am only planning on drilling a very very tiny hole so even if water does come out I can stop it with my pinky. More so it will tell me the seriousness of the problem and if I do need a haul now or can wait till end of season
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  #26  
Old 04-29-2009
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... I am curious and tempted to try drilling a small hole into that platform that the muffler is screwed onto just to see what happens - if it is solid or hollow and if water comes out. What do you think? Dumb idea?
Not sure. You might try it -- but like erps says have a plan.

Maybe take a stroll around the boatyard looking for a similar aperture arrangement, so you can study how the tube seals at the aperture opening. This might give you some better insight into what you're potentially dealing with.
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True - I think I will do both - take a look at other boats and then also try a small pin hole to see. I figured worst case water comes out but since the hole I drilled is so tiny I can easily patch it up then haul the boat. Best case no water comes out and I am able to investigate further with a possible larger hole. If it is a leak in the shaft log I would hope that area under the platform is hollow and so long as there is no water in there I can cut out a section of that platform, locate the leak in the shaft log, and seal everything up. But first I am going to start with the tiny hole. Wish me luck
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Old 04-29-2009
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Sorry, but I do not think you will be able to be 100% sure where or how your leak is located before you actually haul it. Some others ideas of patching for the season, may work, just remember, or consider the removing of any patch that may interfere later. Is it possible that this area froze last winter? If so I would expect to encounter some de-lamination when you get into it. Good luck.
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  #29  
Old 04-30-2009
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A test to perform

Hey Nick,

Sorry to hear of your problem. My boat got splashed yesterday.

If you can get out and sail on a breezy day you can determine once and for all if the problem is the engine or the shaft log. Sail on windy day, turn the engine off, and put the trans in neutral. The shaft should freewheel (assuming you don't have a feathering or folding prop). If you have a leak, it's the shaft. If no leak, then it's the engine exhaust or something like that.

Good luck and let me know if you need a hand testing things.

One last thing, I don't think it will be possible for you to apply anything from under the boat. I doubt you will be able to see where water is getting, and I doubt you could apply anything that would stick and make a seal.

Barry
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  #30  
Old 04-30-2009
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Hey Barry - Congrats on getting the boat in. I'm sure your excited and we def have to have a beer in person one of these days!

Don't know when I'm going to get down to the boat next since the weather is supposed to suck for the next few days but myself and the rigger are going to attempt to finish up with my rigging tomorrow. If I do go down there I figured I would mess around with it a little more but at this point I'm not too worried about it.

Anyway I'm sure I'll see you down there soon

Take care,
Nick
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