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REALLY annoying leak!

Nov 9, 2017
15
Beneteau 42cc 009 Milford
Hi all. I'm new to this forum, so hope you guys can help! My Ben 42CC has a saltwater leak which produces about 4 litres a day. I've traced it to being aft of the engine compartment, doesn't appear to be any stopcocks from anywhere near, leaving I think only the engine exhaust outlet or something to do with the rudder. Shouldn't be exhaust as its above waterline, and I can't see anything around the rudder fittings, which are all glasses in from the top anyway. Any ideas please?
 
Nov 23, 2009
437
Beneteau Oceanis 361 Clipper --
Leak while moving or not? If while moving how about:
- Volvo seal (if any)
- That fitting on the shaft to circulate sea water (if any)
- Mixing elbow

Edit: I read again "4 litres a day". OK, it seems a leak while the boat is not moving. Still, possible to leak except, I believe, the mixing elbow.
 
Nov 9, 2017
15
Beneteau 42cc 009 Milford
Sorry, should have mentioned its leaking whilst just sitting there, and I've checked that the shaft seal (volvo deep sea seal?) is dry. Can't see any leak which is from anything in the engine compartment, including exhaust fittings there etc. It comes in from the " tunnel" from the rear end of the boat which ends up in the engine compartment. I've thought of maybe a plumbers camera shoved up the tunnel? Getting desperate now!
 

JRacer

.
Aug 9, 2011
1,217
Beneteau 310 Cheney KS (Wichita)
You have anything back there that is a through hull but not plumbed, like a depth sounder? What about plumbing hoses like bilge pump/shower bilge outlet hoses running from the bilges to the back of the boat? To test that, I suppose you could put some food dye into the bilge and run the pump to see if the colored water ends up where the water is accumulating. A plumbers/mechanics scope would probably be helpful.
 
Nov 9, 2017
15
Beneteau 42cc 009 Milford
Interesting idea about the dye - will check that out. Depth etc transducers are all forward, don't think there's anything else aft but need to check on the bailer skin fitting
 
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
You have anything back there that is a through hull but not plumbed, like a depth sounder? What about plumbing hoses like bilge pump/shower bilge outlet hoses running from the bilges to the back of the boat? To test that, I suppose you could put some food dye into the bilge and run the pump to see if the colored water ends up where the water is accumulating. A plumbers/mechanics scope would probably be helpful.
OP said it was a salt water leak, but if there is any suspicion of leakage from another system, for this test, napa sells an ultraviolet dye for finding coolant leaks.... it is NON staining. pour it in the water and use a black light to see where the water leaks from... it shows very sharply and immediate with no guessing.
it can be used in any water based liquid... and for oil or fuel leaks, they have dye for oil/fuel based liquids.
 

NYSail

.
Jan 6, 2006
2,702
Beneteau 423 Mt. Sinai, NY
4 litters..... think you would hear it. Do you have a grounding plate on the hull? Beneteau put mine at the stern (423)... maybe that is leaking.
 

JRacer

.
Aug 9, 2011
1,217
Beneteau 310 Cheney KS (Wichita)
OP said it was a salt water leak, but if there is any suspicion of leakage from another system, for this test, napa sells an ultraviolet dye for finding coolant leaks.... it is NON staining. pour it in the water and use a black light to see where the water leaks from... it shows very sharply and immediate with no guessing.
it can be used in any water based liquid... and for oil or fuel leaks, they have dye for oil/fuel based liquids.
Good to know about the UV non-staining "dye".
 
May 17, 2004
3,380
Beneteau Oceanis 37 LE Havre de Grace
Are you sure it’s really coming from the engine area? Just because you see water pooled there doesn’t necessarily mean that’s where it’s coming from. The way Beneteau lays their grid and liner it is possible the water is just running there through the grid. I had a leak from the anchor locker that allowed water back as far as the engine through hull. Admittedly that’s not the most likely, but it might be worth checking around your more forward through hulls and keel bolts just in case.
 
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Mar 20, 2016
479
Beneteau 351 WYC Whitby
Had a leak on mine couldn't find it ,same area behind engine compartment, I could see water under diesel fuel tank. Pulled the boat for winter found it, the tube that holds the cutlass was dripping after haul out around the outside. After removing paint the adhesive that Beneteau used to glue in the tube had 3 cracks in it not adhering
to the tube ,drilled some holes to let it drain. It was a sharp corner to the tube ,will epoxy it and add some matt giving it a good radius in the spring along with new cutlass and Volvo dripless. I also used a dremel to dig out about a 1/2 inch of the glue ,to make sure a get a lot of epoxy with 404 in.
 
Last edited:
Nov 9, 2017
15
Beneteau 42cc 009 Milford
Useful to know about the dye. No ground plate that I know of. I've looked at the rudder as best I can from above and can't see any water. Not sure of the mechanics there, can it maybe be somehow underneath the GRP "casing " that I can see, and still have access to inside of boat? Anything forward of engine area seems to drain more or less directly to the sump in the middle of the boat. I would dearly like to know which points of the boat access the "tunnel " drain that heads aft from engine compartment! My culprit must be along there somewhere! The external shaft entrance point damage sounds possible - can only check that one I guess when boat is lifted in a couple weeks. And no, the leak can't be heard, unfortunately. Please keep the ideas coming - I'm down the boat today to try a couple of ideas!
 
Nov 9, 2017
15
Beneteau 42cc 009 Milford
Thanks Mechone. Ill check around diesel tank for water. It's proving really hard to find!
 

Alfa

.
Mar 19, 2015
25
Beneteau 31 North Vancouver
4 litres/day is a lot of water, but it is possible that this water ingress is through a broken flexible seal around SST stern tube. I think that this tube inside the skeg is only few inches long and is connected to fiberglass stern tube inside the boat where Volvo drip-less shaft seal is attached.

During construction, they pour polyester resin into cavity of the skeg and large volume of resin contracts during curing process creating small cracks. This is not a serious issue, but when seal orotund SST stern tube is leaking, water migrates through the cracks in the resin, collects under Volvo seal then flows forward toward the engine.

When I purchased my B-31 in 2015 I noticed crack and small amount of water in resin filling the skeg. After cleaning SST tube/skeg and applying polysulfide seal I don't see any water inside.
I would not use epoxi resin to seal SST tube to the skeg. Stern tube is vibrating with rotating shaft and flexible transition is probably better and easily to repair if things go wrong. Some older Beneteaus had outside stern tubes made of fiberglass glassed to the skeg. They changed design for a reason.

Attached pics shows my boat: SST stern tube without seal, stern tube with seal and in the process of painting, crack in the skeg resin, fiberglass stern tube with Volva seal. Measuring tape shows distance of crack to Volvo seal.
 

Attachments

Mar 20, 2016
479
Beneteau 351 WYC Whitby
4 litres/day is a lot of water, but it is possible that this water ingress is through a broken flexible seal around SST stern tube. I think that this tube inside the skeg is only few inches long and is connected to fiberglass stern tube inside the boat where Volvo drip-less shaft seal is attached.

During construction, they pour polyester resin into cavity of the skeg and large volume of resin contracts during curing process creating small cracks. This is not a serious issue, but when seal orotund SST stern tube is leaking, water migrates through the cracks in the resin, collects under Volvo seal then flows forward toward the engine.

When I purchased my B-31 in 2015 I noticed crack and small amount of water in resin filling the skeg. After cleaning SST tube/skeg and applying polysulfide seal I don't see any water inside.
I would not use epoxi resin to seal SST tube to the skeg. Stern tube is vibrating with rotating shaft and flexible transition is probably better and easily to repair if things go wrong. Some older Beneteaus had outside stern tubes made of fiberglass glassed to the skeg. They changed design for a reason.

Attached pics shows my boat: SST stern tube without seal, stern tube with seal and in the process of painting, crack in the skeg resin, fiberglass stern tube with Volva seal. Measuring tape shows distance of crack to Volvo seal.
That is exactly what happened to mine. However I disagree with your repair ,mine is a fiberglass tube. They were changed to S/S after complaints from Moorings. Renters towing dinghy's had ropes wrap around props snapping the tube ,thus the change to S/S. The tube holds your cutlass and alignment of the shaft and the torque of your prop. Using polysulfide ,thou stopping the water is allowing the tube to vibrate and flex and thru constant flexing and will in time lead to failure.
Beneteau made it solid in the first place with polyester resin. I,m actually going to give it a good outside rad with mat and epoxy resin making it stronger.
 

Alfa

.
Mar 19, 2015
25
Beneteau 31 North Vancouver
Mechone,
I have seen Beneteau with fiberglass stern tube attached and sealed to the skeg with hard resin. Obviously this works and you should follow this concept.

However, the tube extends from the skeg at least 6" and if demaged by a floating log or a crab trap rope, it could be more difficult/expensive to repair than SST tube fitted in a the skeg and sealed with flexible compound. I expect that this were reasons for design change. Some other than Beneteau sailboats equipped with SST external stern tube are also sealed with flex caulk. Good luck with your project.
 
Feb 14, 2014
5,569
Hunter 430 Waveland, MS
How do you know it is Salt Water? Taste test? Is there a Fresh Water tank or supply line nearby? I have used these pool supply salt water test strips to verify Salt Water versus Fresh[rain] water.

https://www.amazon.com/AquaChek-561...510623227&sr=8-3&keywords=saltwater+pool+test

Does the leak subside with time between engine runs? In other words reduces with time? How do you know it is 4 liters/day? 4 liters per day is ≈1 drop of water every 20 seconds. That is very small drip rate or leak.
_____________
My engine exhaust muffler and hose has probably 20-30 liters of sea water in it [my guess]. You could have a small leak in the exhaust system. If you find your leak is salt water and slows between engine runs, check out your muffler system.;)
_____
I don't mean to interrogate you, but the questions are food for thought.:)
Jim...

PS: One typical drop of liquid is ≈2 milliliter and how Doctors prescribe eye drops.
 
Nov 9, 2017
15
Beneteau 42cc 009 Milford
Mechone and Alfa, thanks for those ideas - I will have a close look for cracks in that area. I suppose if all else fails, once I get the boat out, if I still haven't found the leak it will presumably show drips from that area! I've checked around aft tanks as best I can without moving them, removed boxing around exhaust outlet, all to no avail. Tested salt water by tasting and also by leaving thin residue on a mirror, with a freshwater sample also - the salt water left residue and the fresh didn't
 
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Nov 9, 2017
15
Beneteau 42cc 009 Milford
Hi guys thanks for your help up to now. The good news is I've found the leak! It is around the shaft as mentioned above. FYI, I found leak by getting different coloured food dyes, and had a diver friend squirt this with a syringe around the suspect areas. Detected this in internal leak area behind shaft. Boat now on hardstand, and water now dripping from skeg where shaft enters. My problem is that its in Spain, a marina with little local expertise, so need advice please as to exactly what to do. 20171202_140729.jpg 20171202_140729.jpg 20171202_140722.jpg
 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
That shaft brace device indicates that some kind of repair has been effected on the propeller shaft. It was not original. Have it removed and the shaft tube cleaned back to the strut body. The strut body is solid composite and not easily damaged but that shaft tube could be cracked or separated from the strut body. The repair would require the services of a skilled composites technician. Be a good time to have the shaft removed and checked for true. Work with Beneteau FR to assess the situation.