How much fuel fumes is normal?

[OrionDart]

Hi all, I am a new boat owner which has come with an atomic 4! I am curious if all the nay sayers online just have me overly nervous or is this normal. Before I start up, I poke my head in the engine compartment and smell a little bit of fuel fumes. It’s not overly strong at all. I then pop the bilge cover off and sniff down there and I smell nothing. I run the blower for minimum 5 minutes before starting, however last time I put my nose right up against the blower outlet after 5 minutes and I still smelled a faint hint of fumes. I kept it going for another 5 minutes and same. I don’t really see any evidence of a fuel leak I don’t think. When I took delivery I had the boat yard clean out the fuel tank, replace the fuel lines, and rebuild the carburetor.

So my question is, is this a case of an engine just being an engine and you’ll always have a faint hint of fuel, or am I looking for it to be completely rosey and smelling like fresh air? Again the fumes are faint, it’s not a slap you in your face smell and honestly has me second guessing if I really am smelling fuel, but I think I’m just super worried because of stories I’ve read online and I honestly don’t know much yet. So what is the professional consensus?

[Al Schober]

I'd recommend that you have a few of your friends at your marina give your boat a sniff. Odors are such subjective things. The first sniff when you open the hatch or lift the floorboard is the most telling.
When we bought our first 'big boat' with the inboard, the Admiral insisted that I install one of those fume sniffers. In 30 years, it sounded off twice - neither time due to the engine. First time was due to a fuel jug for the outboard stored in the lazarette. It had gotten onto it's side during some of that port/stbd stuff and had a slow drip from the cap. Second time was during fueling. I thought the tank had developed a leak but the culprit was the old fill hose from the tank to the deck - crumbled in my hand!
Cleaning the tank and replacing the fuel lines were good steps. Did the yard check/replace the fill hose?

[Dave Neptune]

What Al said and check the fittings. IE give the fuel lines a twist near the clamps and see if they twist.

Also run your finger under the carb and around the scavenge tube and fuel pump while running or just after.

Note if the yard did a lot of fuel related work a spill is not out of the question and fuel smells can linger around oily or greasy things as well as permeate some surfaces.

Dave Neptune

[JOHN COOKSON]

Before you start the engine after it has been not started for a day or so take the back flame off and check for gas in the carburetor throat.

ex TRUE GRIT

[OrionDart]

I'd recommend that you have a few of your friends at your marina give your boat a sniff. Odors are such subjective things. The first sniff when you open the hatch or lift the floorboard is the most telling.
When we bought our first 'big boat' with the inboard, the Admiral insisted that I install one of those fume sniffers. In 30 years, it sounded off twice - neither time due to the engine. First time was due to a fuel jug for the outboard stored in the lazarette. It had gotten onto it's side during some of that port/stbd stuff and had a slow drip from the cap. Second time was during fueling. I thought the tank had developed a leak but the culprit was the old fill hose from the tank to the deck - crumbled in my hand!
Cleaning the tank and replacing the fuel lines were good steps. Did the yard check/replace the fill hose?

Hah so my next problem then is making friends at the marina! I’m still new over there. When I first open up the hatch, it’s not overwhelming, I haven’t had issues, but I just want to make absolute sure. I’ll have to try to snag someone.

No, they did not replace the fill hose. Didn’t think of that one, wish I had. Thank you for your response!

[ndutton]

Q: How much fuel fumes inside are normal (more like safe)?
A: Zero

You should have no smell inside the cabin when the engine is running AND at rest. None, not a little bit, not "it doesn't smell like that much." Be sure to smell the bilge too because gasoline vapor is heavier than air.

[zellerj]

For 20 years I have never smelled gas. And then during one particularly robust sail, I could smell gas odors coming from the cabin. Only happened on starboard tacks when the port side was the low side. I did not start the engine until I knew the fumes had cleared. Nothing around the engine was leaking. I finally found a gas tank vent line was cracked, and the port side heal caused gas to leak from the vent line, which was on the top port side of the gas tank. Easy fix and now I am fine again.

[JOHN COOKSON]

\ . When I first open up the hatch, it’s not overwhelming, (?), but I just want to make absolute sure.

Agree with Neil. You have a very big and serious problem to deal with.

ex TRUE GRIT

[joe_db]

The safe amount is NONE.

[Larry in Maine]

Gas Fume Detector

Anyone have recommendations regarding a gas fume detector? There is one on my boat but it is very old and disabled. I don't think that sniffing around prior to starting my A4 is sufficient.

L Starr
Camden, ME

[msmith10]

No experience with gasoline vapor detectors, but in my experience, my nose is more sensitive than the electronic detectors I've seen. I can smell natural gas long before detectors in my home start to alarm, and I can detect the gasoline smell without even a liquid leak- just from vapors when there's an opening in the fuel system.
Certainly there's no harm in an electronic detector, but I think your nose is more reliable.
I would, however, strongly recommend a CO detector. You can't smell that, and they're cheap.

[ndutton]

I completely agree with Mark including a detector is a good redundancy. Mine is a now-discontinued Xintex unit that interfaces with the bilge blower, some of their current models do also.

[W2ET]

Everyone should be conversant on the signs and symptoms of carbon monoxide poisoning. It's a silent killer. And your nose won't help.

Bill

[joe_db]

I have a CO alarm. I would *never* want to have a boat with an enclosed cabin with no CO alarm, people sleeping below while you are underway could possibly not wake up. It isn't just engines, gas (propane/cng) stoves and heaters can make CO as well.
I have been CO poisoned by an airplane with a leaky heater and it was not fun at all.

[tenders]

Early stage rust-through in steel fuel tanks can also create mysterious gas fumes. My tanks each lasted 21 years before rusting, and then I got a stainless tank, which I expect to solemnly pass on to my great-grandchildren.

Are your tanks painted steel, and do you know how old they are? Mild steel tanks are not particularly expensive to custom fabricate, and they may or may not be difficult to replace when empty.