361 mystery leak

[tnathan]

we sailed our boat down the bay last week after having her on the hard for the winter. After two days of sailing I didn't notice any water. I went back on day three after we were done to clean her up and found the prop, engine and battery bilges full. I cleared the water and have been checking daily and keep finding water. I read some posts on here and have eliminated the engine water intake, and prop seal. I found water under the fuel tanks. I then thought it could be the stern shower or rudder, but they too were dry. So there is water leaking down the middle of the boat but not touching the wood bulk heads (no discoloration on any of the wood bulk heads). I then happened to look under the swim platform and found the rear dam between the rudder post and transom was full of water.

So, it could be the hull deck joint under the swim platform. But this seems unlikely given how strong the hull deck joint looks built to me and it seemed to have gone bad rather suddenly rather a progressive issue.

Or it could be water from somewhere else or from the winter layup that sloshed into there but nothing seems to be leaking, the bulk heads all look dry and I didn't notice anything when checking the engine before we sailed on day 1 and 2. How could water get that high up in such an odd place?

The area looks pretty sealed without any through holes. Is there anything else that runs back there between the hull and swim platform that Could,be,filling this area up.?

 

[Philip_Oceanis 361]

Are we talking about fresh water or sea water? If the latest then check throughulls, volvo seal or that nippon thing at the shaft. If fresh water probably water tank, water tank hoses, stern shower, rain water from openings eg shore power, the place where the blower is etc (there should't be of course any opening). One more thing i can think of is any water hoses going back there that have cracked for some reason. The shower one for instance ends back there (starboard side of the stern). I don't know. But please let us know when you solve the mystery.

 

[tnathan]

fresh or salt? That is hard to say. I did taste it and it was slightly salty. So I guess salt but wasn't sure if you could get some salty taste just from sloshing around in the bilge. Not a connoisseur of bilge water.

Through holes: that doesn't seem likely since they are all lower in the boat than the swim ladder. It seems to be filling the swim platform dam then it overflows and drips into the shaft bilge then when it overflows that it ends up under the engine, when it overflows that it ends up under the battery. The through holes all seem dry but there is moisture along the centerline of the boat stretching from the swim platform to the shaft bilge.

fresh water/swim shower: I thought it could be this but again the hoses are all dry. The starboard lazerette where the water tank sits is all dry. And, the bulkhead between the engine and water tank is dry and shows no staining. The same for the swim shower I pressurized the system and looked for leaks and any signs of water in the starboard rear lazzerate. Nothing. The bottom of the locker had some dry leaves laying there. And, it has been wet, 70 and raining here for the last week so it isn;t likely it was leaking but the trail dried up. Nothing is evaporating.

Rudder: When the fresh water system/swim shower seemed to not be the issue. I stuck my head in the locker to look at the rudder. I thought to myself: centerline water, not touching any of the wood bulkheads on either side, higher than prop seal, behind prop seal. . . ah, its the rudder. But when I looked at the couplings and the shaft there was no water that I could see around the rudder. Then as I was trying to get out of locker I happened to look back and saw water had pooled in a little dam on the inside of the hull under the under the swim platform. It was sort of full and looked like as the boat rocked a little would splash out and run down the middle of the boat and through the two holes where all the tubes run through into the engine compartment
.
So how is it getting up there? (1)Hull deck joint under the rub rail? My theory but seems unlikely give how strong that deck joint is. (2) Somewhere completely different and maybe as we sailed we ended up stern down long enough for water to get caught back there. But if there was enough water and motion to do that, I would think I would have found signs of water all over (stains on wood, etc.). (3) maybe a transom through hole as you suggest. I will take a look at that theory.

 

[Benny17441]

Slightly salty seems like your leak is fresh water. Not a connoisseur but have swallowed enough salt water to know that its concentration is pretty darn salty. If you have ruled out any leaks from the shower fixture it is likely a rain water leak. Get a water hose from the dock and spray over the cockpit and the swim platform and check below soon after to see if you can detect where is it coming from. Check the cockpit, swim platform lockers and deck or any scuppers or built in channels to divert rain water. Coming off a winter layup some of the seals and joints may have temporarily lost some of their ability to perform so If you cannot detect anything give it some time to see if it continues or not.

 

[tnathan]

True, but I am on the middle Chesapeake. So we expect we less salinity than you. I guess it will be an iterative process. On the 361 I just have a hard time seeing how water would get into the space between the swim platform and the hull. It is pretty high and awful far back. As someone else mentioned I need to just place paper towels in different places and see what gets saturated to eliminate causes one by one.

Actually that's how I eliminated the engine and Volvo dripless seal. I wrapped a paper towel around the throttle cable that runs up and to starboard of the prop seal. I came back two hours later the paper towel was soaked but there was no water in the prop bilge or the engine bilge. That lead me to look in the hole in the middle of the gas tank where I found water, which led me to the prop, which led me to the dam under the swim platform.

I was hoping someone would say "that's a well-know issue with 361s and the likely issue is ..." But it seems that I have something unique and will have to keep eliminating causes. tracing it with paper towels.

Thanks for all the great advice.

 

[Philip_Oceanis 361]

I was hoping someone would say "that's a well-know issue with 361s and the likely issue is ..." But it seems that I have something unique and will have to keep eliminating causes. tracing it with paper towels.

Thanks for all the great advice.

Luckily (well, for the rest of us at least) this is not a well-known issue. Once you sort it out you will in general be finding only dust around the boat!
Just a crazy idea, since this mystery drives you crazy anyway......is the cap to get to the rudder stock closed properly? You know, the one below the helmseat. Any water getting in the boat from there will flow to the area you mentioned.

 

[tnathan]

thanks. That's a great idea. I never touch that thing. I will take a look. Thanks.

 

[Tejas]

Might not be helpful in this case, but a swimming pool pH test kit can be useful for identifying the source, or eliminating the source, of water.

 

[Bill Roosa]

OR you could just use your finger and toung to tell salt from fresh water. a swimming pool pH kit is what we called in the military "pole vaulting over a mouse turd"

 

[tnathan]

Water still tastes slightly salty. Since I am on the bay, the water is brackish so its hard to tell if it is fresh/rain water that ran over a dirty surface and picked up some salt or seawater. I am leaning towards seawater. Still haven't found the leak, but appreciate the advice.

My access cover to the emergency tiller was on but loose enough that I could open by hand. Didn't see any water there but it was a good suggestion to check. I cleaned the o-ring and tightened down with the wench handle enough to compress compress the o-ring. Frankly this seemed unlikely in my mind since it sits above the swim plat form and is covered by the captains seat and a bimini.

I also tightened all the swim shower water fittings. I have never found any moisture there, but thought it was an easy thing to do just to eliminate the easy causes.

After removed the water from under the swim platform, it has stayed pretty dry. I found about a cup or two back there and another cup around the rudder post. I am getting about 1/2 gallon in the prop bilge. Using paper towels it still seems like it is coming from under the fuel tank.

I am going to focus on the swim ladder and the rudder now. I didn't find any moisture around the rudder (except some pooled at the bottom of the rudder post. Does anyone know where the likely trouble spots are with the rudder so I could wrap with paper towels to see if I can catch it leaking? You have a fiberglass base, with an autotiller hydraulic arm at the top. Are there some spots I should check?

 

[Philip_Oceanis 361]

Do you find the water after you move the boat or you clean everything, come back after some time and the water is there? I dropped the rudder some years ago and really cannot see how water could enter through the rudder tube. Certainly no way to climb up where the top bearing is, too high! How about the point where the exchaust exits the hull? It's above the waterline but can get under the water quite easily when motorsailing with some angle.

 

[tnathan]

I am having a hard time finding the pattern. It was hauled out and just put back in.

We never noticed any water last year or when I did a pre-departure check for day one. We motored her to a new marina on day one last week. On day two, I checked the engine during my pre-departure check and found nothing. We did some sailing on day two, but didn't check the engine when we left. On day three I came back to do some clean up and opened the engine compartment and there was enough water to fill the battery bilge, engine bilge, and prop bilge. I sopped all of this up which was around 8 gallons total. Since then I am getting maybe a gallon or two per day.

It has been raining like crazy out here the last two weeks; I did wash it down; I did sail her; I did run the motor; I did pressurize the fresh water system. So it has been hard to eliminate causes.

As for the rudder, it is in a area that the leak could be from: centerline and behind fuel tank. As you mention it does seem high and I don't see any sort of packing gland that needs to be tightened or any signs of leakage. But, I thought I would ask. Beneteau's manual recommends annual overhauls of the rudder but didn't clarify what that was exactly. I thought I would ask to see if there was something I should be doing with the rudder from a maintenance standpoint (e.g. tighten a packing gland). I recall some folks said the 361 rudder is essentially maintenance free. Some said they grease it; others say the leave it alone as the grease is a magnet for dirt.

You make a good suggestion. Day one we mostly motored due to weather; Day two was when I noticed the worst water problem and that was when we sailed. I keep looking at the through hulls and don't see any moisture. Maybe the leak is in the tubing. Perhaps with some heal we were filling one of the throughholes with sea water which filled one of the tubes and got trapped . There could be a small hole it is leaking and wicking along the tube and into the bilge. Something else to check. Thanks.

 

[Gunni]

Nathan, you do know don't you that we got something like 6 inches of rain on the bay last week? It was a test of all your deck fittings, ports, hatches ....and your companionway - that last one is as close as you find to "notorious leaker".

 

[Philip_Oceanis 361]

I keep looking at the through hulls and don't see any moisture. Maybe the leak is in the tubing. Perhaps with some heal we were filling one of the throughholes with sea water which filled one of the tubes and got trapped . There could be a small hole it is leaking and wicking along the tube and into the bilge. Something else to check. Thanks.

As I am sure you have noticed there are a few plastic thoughulls just above the waterline in both sides at the stern of the boat. Hoses from the heads shower, lazarettes etc end on them. Check very careful if any of these plastic ones are broken (because of the sun, or probably somebody/something hit them etc). Even if the hose at the back side may look fine if the actual through hull is cracked it will let water in the boat while the boat heals. They are all above the water line so don't worry even if you break them and must replace them.

As far as the rudder is concern, it has a bronze bearing at the bottom which you must NEVER grease and a nylon top bearing that you grease when you drop the rudder and have access to it.

 

[Povil]

Hi tnathan,
Did you ever find the source of your leak? I have a 361 and it is leaking from the stern down the center line under the fuel tank into the prop shaft bilge. My leak is definitely rainwater since the boat is on the hard and fills up after a rain.
I have paper towels all over the place and the only place it's wet is on the centerline. Slowly loosing my mind!

 

[tnathan]

Povil,
Not really. Last year after a few weeks the leak seemed to go away and not return. I drove myself crazy trying figure out where it was coming from, but it finally went away on its own. I thought maybe it could have been 6 months of condensation under the shrinkwrap that took that long to work its way down to the bilge. I also had the Volvo penta shaft seal replaced this year. I found water for the first few days after we relaunched this year but it dried up and seems fine now. So why? I think my issue could be that the folks last year didn't do a good job with dehumidification bags. Or, it could be that the prop seal was dry old rubber and leaking. I wonder if the rubber seal absorbs water and expands when in the water and the new seal I bought tightens up faster???

In any event, I seem to be in better shape this year. Not sure why. I would recommend starting with the easy stuff and burp your shaft seal and see if that does anything. After that you are into the iterative paper towel diagnostic. Start on one end and work your way to the other. Inspect the water in the bilge and see if it is salt or fresh. Try emptying your rear water tank and see if that makes a difference. Same with the stern shower. Check the raw water pipes couplings. The issues I was afraid of was the hull seal between the top and bottom molds or the rudder post, which I would have to haul out to fix. Luckily for me it didn't turn out to be either of those.

Good luck.