Rotten egg/sulfur smell

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Moonfish

Moonfish

Guru
Commercial Member
Joined
Nov 19, 2011
Messages
1,586
Location
USA
Vessel Name
Traveler
Vessel Make
Cheoy Lee 46 LRC
It stinks! :mad: About two weeks ago, we started to notice a rotten egg smell on our Cheoy Lee 46. The smell is basically confined belowdecks in the aft cabin and aft staircase landing area. It's not the hot water, nor the cold water, either. Running both anywhere on the boat gives off no odor. And the smell is not in the adjacent engine room.

We noticed the odor about the time we pumped out (which is every two weeks). Neither the aft or fwd head smell, though. And the holding tank is located under the floor in the fwd cabin. No smell there, either.

The best possible source we can so far identify is when we lift the floor hatch in the aft staircase landing just outside the aft cabin and engine room doors. The aft fuel tank access plate is there, and the smell seems to be the strongest at that point. It's a 220 gallon tank that feeds the day tank for the two diesel heaters. There isn't any apparent fuel leaking, as the tanks are made of fiberglass and integral to the keel. There is no way to sound that tank (we can sound the 620 gallon fwd fuel tank), but I am surmising the aft tank may be close to empty.

Can a mostly empty diesel fuel tank give off a rotten egg smell - outside of the tank? My wife put her super sensitive nose at both the aft tank vent line and the deck fill, and all she can smell is a normal "diesel odor".

Oh, and the odor seems to ebb and flow in strength. Some days it is really strong, and others less noticeable. Any ideas? :confused: Thanks!
 
Have you checked your batteries. I boiled a cell dry a few years ago and it smelled like rotten eggs from the sulfur.
Dave
 
^^^^^+1
 
Thank you for the ideas. All batteries are fine, and we have Vacuflush heads that are plumbed fresh.
 
+2
Overcharging batteries will create the odor.
 
Shower sump? They can get funky.
 
Brand new (8 months old) Magnum Inverter/charger. I monitor them, and they are not overcharged. However, the shower sump is something I will look into!
 
Have had that odor several times over the years traced to HW tank.
 
Maybe the kids didn't find that Easter Egg you hid under the tank?

Check the other stuff, if you don't find the source come back to the batteries.
Sulfer smell = Sulfuric Acid = Batteries
Maybe one cell is going bad.

Has anyone ever used one of those infrared thermometers to check for a bad cell in a battery? Seems like there would be a temperature difference between a good cell and a bad one.
 
Opening the shower sump and giving it a spray of bleach solution might help!

Dave
 
HopCar said:
Maybe the kids didn't find that Easter Egg you hid under the tank?

Check the other stuff, if you don't find the source come back to the batteries.
Sulfer smell = Sulfuric Acid = Batteries
Maybe one cell is going bad.
Click to expand...

That's so funny, because we wondered if in fact we had forgotten one Easter egg! Both my wife and I remember counting them that morning, and accounting for them all. Plus, we've looked everywhere the odor is and can't find anything "rotting". I even using a mirror tool to look under the floor and behind tanks. Nada. We thought maybe a dead mouse, but again no carcass.

Batteries are all good, every single cell. Just checked. Plus they're all in the engine room where there is no bad smell - just engine room odors.

The hot water tank is in there, too. It's newer (an IsoTemp unit that's just a few years old) and is just fine. No odor at the tank or in the hot water when running it. We had that problem, though, on our last sailboat with an old, corroded hot water heater. We'd get stinky water at the taps...

Anybody have experience with a nearly empty diesel fuel tank producing bad sulfur smells? We have a dock neighbor who thinks that is the culprit.
 
Moonfish said:
It stinks! :mad: About two weeks ago, we started to notice a rotten egg smell on our Cheoy Lee 46. The smell is basically confined belowdecks in the aft cabin and aft staircase landing area. It's not the hot water, nor the cold water, either. Running both anywhere on the boat gives off no odor. And the smell is not in the adjacent engine room.

We noticed the odor about the time we pumped out (which is every two weeks). Neither the aft or fwd head smell, though. And the holding tank is located under the floor in the fwd cabin. No smell there, either.

The best possible source we can so far identify is when we lift the floor hatch in the aft staircase landing just outside the aft cabin and engine room doors. The aft fuel tank access plate is there, and the smell seems to be the strongest at that point. It's a 220 gallon tank that feeds the day tank for the two diesel heaters. There isn't any apparent fuel leaking, as the tanks are made of fiberglass and integral to the keel. There is no way to sound that tank (we can sound the 620 gallon fwd fuel tank), but I am surmising the aft tank may be close to empty.

Can a mostly empty diesel fuel tank give off a rotten egg smell - outside of the tank? My wife put her super sensitive nose at both the aft tank vent line and the deck fill, and all she can smell is a normal "diesel odor".

Oh, and the odor seems to ebb and flow in strength. Some days it is really strong, and others less noticeable. Any ideas? :confused: Thanks!
Click to expand...

Darren,

Not sure if this will help, but worth checking out. On your Pacific NW Boater site, you featured a Rescue Tape application where you fixed an exhaust water leak, inboard
The transom. We experienced the same issue on our CL 46, on the port side. The water drains under the aft cabin berth, and surrounds the rear fuel tank. Had to use an 8' extension on my wet vac to get all the water out. And, I did find water under the hatch right outside the engine room door. Stale, salt water can smell very bad. Might be worth using a flashlight to peer into the dark space under the rear cabin.

Will be looking out for our sistership, Traveler, this summer.

Good luck,

Mark
 
Does your holding tank have one of these, if so it may need changing?
 

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I just diagnosed this same smell for my inlaws recently (in their home). Turned out to be a bad anode inside their water heater. In their case given the age of the unit, it was more cost effective to replace the water heater than purchase a new anode for it.

Good luck.
 
Rotten egg smell is from hydrogen sulfide (H2S). It is detectable by smell at under 2 parts per million, so it doesn't take much to create a stink.
**Be careful poking your nose around though, this gas is fatal when the concentration gets to about 1000ppm.

Most of the above posts are possible sources. The H2S is produced by bacteria. SRB's (Sulphate Reducing Bacteria) which breed in old diesel or stale water. These little fellas will produce hydrogen sulfide as a byproduct. Besides the smell; another problem is the H2S they produce is very corrosive to your fuel tanks.
Bleach works well to kill them in water, and use a good diesel fuel treatment product in your tanks.
BTW- they will live in diesel only if there is a trace of water.
They are also anaerobic, so it won't be the old sandwich under the fridge if there is a supply of oxygen.
 
Last edited:
this kind of gas?

Nobody asked if you have any propane on board. Even the small throw away tanks could be the culprit. I have noticed on my BBQ they are most susceptible to smell when they are empty. A tank seems to depend on pressure to seal itself. Propane is heavier than air and always flows down into the bilge. Just a pin hole in a copper line could do this.
 
I agree with uncle bob..propane is naturally an oderless gas and the rotton egg smell is added to it so that you KNOW you have a leak. If you have propane at all get a sensor in there and check for leaks.it will fill your bilge until it reaches an open spark or flame.
 
last year I had the same odor and it turned out to be a faulty pilot light in the oven...the gas sank into the bilge causing an awful stink.not to mention the danger.
 
Yes - good call Bob & Tangler.
The smell of the odorant (ethyl mercaptan) used to give propane its stink is very similar to hydrogen sulfide. Most people cannot tell the difference.
 
So Moonfish,
What was the cause of the smell?
just curious.
 
A pilot light on a boat is a very bad idea. Next to a gasoline leak, propane is probably the best way I know to blow yourself up. I think you will find that you will fail a survey and probably a safety inspection with pilot lights on your boat, not to mention your insurance company, which will use every means to wiggle out of a claim.
 
A bad battery or charger cooking a battery will give off the same smell.
 
My batteries get an egg smell.good luck.commen smell for them...
 
>A pilot light on a boat is a very bad idea.<

Really?

Most insurance co dont mind propane a bit , and most modern pilot lights have a no flame shutoff.

If course it is possible to create a milti failure scenerio , but if they were common the number of gasoline boats would not be 100 times as many diesels.

Do not fear what you are not familiar with ,
 
Wxx3 said:
So Moonfish,
What was the cause of the smell?
just curious.
Click to expand...

Sorry for the delay, just saw this thread crop up again. So about two weeks after the smell appeared, it simply went away. A little disconcerting that we were unable to identify the culprit, but happy enough that its gone...

Mark's theory about saltwater settling on that side of the boat (probably alongside stringers) from the leaking exhaust fitting seems the most probable. As for other theories, the holding tank is at the other end of the boat, and there is no propane in the vicinity. Even if there was a propane leak that settled into the bilge, it would not have been so localized on just the starboard side away from the bilge(s). And the batteries with a new smart charger are in the engine room and far removed from the small area that smelled.

Appreciate the ideas, though. Thanks!
 
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