Salt Water leak - only when sailing

Delfini

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Im hoping someone can give me an idea how to find where the salt water is coming from when sailing - with all sea cocks open and alongside in the marina with the engine and prop engaged for 30mins or more its a dry as a bone - when I go sailing in fairly gentle conditions I come back with 10 buckets of salt water in the bilge

Keel and keel bolts are 100%

Is there any recommended technique or maybe I must lift the sole boards whilst sailing and see what happens ?
 

Robin

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Was the boat heeled when under sail? Is there water in one section of bilge or more? Could the heads be siphoning over into the bilge under sail? Is the rudder tube allowing water up past any seal when under sail heeled?
 

Sandy

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How often has this happened, what were the conditions, where is the water (one cabin or all). I would be lifting the sole before moving the boat again.
 

VicS

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Any outlets , eg from galley sink or heads wash basin, that are only just above the static water line but likely to be dipped under when sailing?
 

lustyd

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First step is to rule in/out the seacocks by sailing with them all closed. If that's ok then open one at a time until you find the culprit. If it happens with them all closed then this thread will be much shorter!
 

Delfini

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OK sorry - its a 48foot Swan with loads of holes roughly 100mm above the water line that get dipped when sailing - 10 buckets equates to about 1 inch of water - haven g checked no leaks from the engine cooling system and the prop seal I thought it was one of these holes above the water line and the bilge pump was my favourite even though it has a good anti siphon loop in the outlet - the rubber flapper valves in the whale gusher pump were not very rubbery and the seat very badly corroded and possibly not keeping any backwash water out when heeled over - however I replaced the pump last week and the same amount of salt water came into the boat yesterday during sailing - as before absolutely dry on the mooring before we went out

Maybe I should bung up the holes joining various bilge sections as the water finds its way to the deepest part of the bilge where the strum box is situated and I can't tell where its coming from unless I ask someone to watch for ingress when sailing - maybe thats what I will be forced to do but I hoped there might be a recommended procedure
 

lustyd

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Don't bung up the holes, they're there for a good reason! You just need to be systematic in your approach. You only need one cock open for the engine to get started, and then gradually open up others through the next trip until water appears. It it were me I'd find somewhere sheltered that I could tack back and forth on a beam reach to test both tacks. As I said though, you don't seem to have confirmed it's a seacock issue yet and that would be first on my list - it wouldnt' be the first boat to have a hole in the hull under the sofa! It's entirely possible the ingress is in the chain locker or similar.
 

Delfini

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Don't bung up the holes, they're there for a good reason! You just need to be systematic in your approach. You only need one cock open for the engine to get started, and then gradually open up others through the next trip until water appears. It it were me I'd find somewhere sheltered that I could tack back and forth on a beam reach to test both tacks. As I said though, you don't seem to have confirmed it's a seacock issue yet and that would be first on my list - it wouldnt' be the first boat to have a hole in the hull under the sofa! It's entirely possible the ingress is in the chain locker or similar.
I don't quite know why it would be a seacock issue if there is no leak when the boat is alongside with all seacocks open - do you believe there is some additional stress when sailing ?
 

bikedaft

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Borrow a friend to stay down below, or autopilot and quiet sea.

Remember e.g. gas locker drain etc (that nearly sunk my Dad!)
 

Daydream believer

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Does the anchor locker have drains above the waterline that are below when under way? If the anchor locker is not properly sealed wate in it could then run through to the saloon etc.
To test this tape up the drains & fill the anchor locker with a hose & see if any water does stay in the locker or goes into the boat.
I have a drain & one day it shaved a piece of wood off the pontoon when I left. This blocked the hole. In rough water that followed the locker filled up & then overflowed into the forward berth soaking the mattress. Then ran into the saloon doing the same to the seating. Took ages to understand where the water had come from, because it drained slowly away before we spotted it.
 

Delfini

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Does the anchor locker have drains above the waterline that are below when under way? If the anchor locker is not properly sealed wate in it could then run through to the saloon etc.
To test this tape up the drains & fill the anchor locker with a hose & see if any water does stay in the locker or goes into the boat.
I have a drain & one day it shaved a piece of wood off the pontoon when I left. This blocked the hole. In rough water that followed the locker filled up & then overflowed into the forward berth soaking the mattress. Then ran into the saloon doing the same to the seating. Took ages to understand where the water had come from, because it drained slowly away before we spotted it.
Yes the anchor locker does have a drain above the water line which gets wet when sailing as do lots of drain points above the water line (including the basin in (both) heads , water maker dump , sink in galley, gas locker, bilge pumps etc)

When I first got the boat in 2019 I couldn't understand why stuff in the cockpit lockers was getting wet when sailing - we dried everything a couple of days in a row before we found a shut off valve in the locker drain tube in the aft lazarette - sea water was flowing up the drain to the locker when heeling - thats why I am not too worried about the water in the bilge - I think (hope) it will be an easy fix when I can find the culprit !
 

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Hope its something as simple as a throughhull letting water in. Do they all have seacocks or valves to isolate them in turn?
I had something similar a few years ago. Not as much water but it only came in when sailing hard. Eventually tracked it down to the rudder tube weeping when sailing hard (I've cured the bad weather helm that put so much strain on the post.) It had a crack at the base. I ground it out, repaired the crack and beefed up the rudder tube substantially.
 

RupertW

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I don't quite know why it would be a seacock issue if there is no leak when the boat is alongside with all seacocks open - do you believe there is some additional stress when sailing ?
My most complicated leak was through a seacock and happened for the first time after 9 years of owning the boat - happened when the boat was heeled over hard in one side. It was a siphon rather than a leak but kept filling the bilges over the floorboards even with auto bilge pump plus hand pumping. All seacocks looked fine - no splits, no leaks, no overflowing sink or toilet bowl just invisibly siphoning water into the bottom of the fridge (as we eventually worked out but could not see as the fridge was full of food and the fridge had always had an opening so condensation drained to the bilges.
 

Spirit (of Glenans)

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Im hoping someone can give me an idea how to find where the salt water is coming from when sailing - with all sea cocks open and alongside in the marina with the engine and prop engaged for 30mins or more its a dry as a bone - when I go sailing in fairly gentle conditions I come back with 10 buckets of salt water in the bilge

Keel and keel bolts are 100%

Is there any recommended technique or maybe I must lift the sole boards whilst sailing and see what happens ?
I had a similar problem with my boat. I always sail with only the engine seacock open. Water was appearing in the region of the keelbolts after sailing but not after motoring. I suspcted the keel bolts. The keel was dropped and resealed. Still no change. I noticed that the water only seemed to appear after sailing on port tack. I eventually found that there was a small leak around the heads outlet skinfitting (on starboard side), which was only just submerged when on an even keel, out of the water when on starboard tack, but quite well submerged, thus under much greater pressure when on starboard tack.
The crucial technique I used to detect the source of the ingress of water was use of that cheap blue wiping paper found on service station forecourts. Blue paper hand towels can also be used. They show up wetness with a dark stain.
 

lustyd

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I don't quite know why it would be a seacock issue if there is no leak when the boat is alongside with all seacocks open - do you believe there is some additional stress when sailing ?
Most of the posts above were about issues from seacocks and their associated plumbing. If you close them all then go sailing then you can rule out a considerable number of systems because there are then no "known" holes in the bottom that might be causing ingress whether locally or through the pipes. Once you rule out the known holes, you're left with either unknown holes on the bottom or known holes on the top. This is easier to troubleshoot and has fewer variables. Someone mentioned the heads syphoning, which can be ruled out quite easily by closing the heads seacock.
 

TernVI

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Assuming the OP's idea of gentle conditions doesn't involve much water on the deck or the gunwhale getting immersed, we can rule out many of the usual suspects.
10 buckets, 100 litres, is not a small amount.
It should be easy to see where it's been.

The cabin sole needs to come up to get everything clean and dry.
Then go sailing and break it down into areas you can rule out.

I had one leak on a boat, only apparent after sailing, but it was rain water. Turned out rain was pooling under a tank and got tipped into the bilge on port tack.

Blue paper towel is a good tool, as is talcum powder. Talc shows where water has trickled.
Just be aware that water doesn't always take the direct route from A to B.
So the best starting point is to have everything dry as a bonio.

Break it down. Front or back of boat? Port or starboard? Then every hole in the GRP is a possible source.
It's probably time every hose and seacock had a 'coat of looking at' anyway.
 

geem

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It sounds to me like one of your skin fittings above the waterline has a leak when they submerse. It shouldnt be too hard to find if you have so much water coming in
 
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