fuel vent/smell question

Indy1830SS · Jul 2, 2008

I've search the forums for posts about fuel smells....and I get it, all gas smells are to be taken seriously! But I still have a question. What is normal? Will the fuel vent always provide a detectable vapor smell even when all systems are go?

I have a 1994 Chaparral 1830 4.3LX Merc. Everything works great. I smell a vague gas odor when I untarp on the trailer, and on ocassion while just floating around. Nothing like raw gas...just vapors. It isn't unlike what I have experienced around other boats...but never paid that much attention until it was my boat.

So, I guess my real question is whether or not I should detect any fuel smell at all...ever, and if so where from? There is something that looks like a vent in the floor circa the ski locker that I have always assumed is the fuel vent...thus I always thought this was a normal smell.

Thanks,

Zack

jerryjerry05 · Jul 2, 2008

Re: fuel vent/smell question

Your fuel tank should vent to the outside of the boat.If it is vented to the bildge it could cause an explosion.Check the fill hose and connections.Follow it to the tank and check the vent line from the tank to the hull.Check the gas line from tank to motor.Check for old/cracked hose.Find the vent and see if when covered it's under the storage cover.Check the motor while running and check the return line from carb to the pump.
When you have the boat at home on the trailer pull the plug and raise the bow and see what comes out the transom.
You really shouldn't smell gas in the boat.Jerry

QC · Jul 2, 2008

Re: fuel vent/smell question

To answer your question, yes, you will smell gas from your tank vent if there is fuel in the tank and this is absolutely normal and acutally confirms that your vent is working . . . The vent line goes directly to your tank, so it has to smell of gas. Also, while filling you should "see" a steady stream of "invisible" vapor exiting the vent to the OUTSIDE. The vent will NOT be in your floor.

Indy1830SS · Jul 2, 2008

Re: fuel vent/smell question

OK - thank you gentlemen for the comments. It sounds like I should be able to isolate any fuel odor to the vent...guess I haven't paid that much attention to where it is on the hull, but I'm sure I can find it.

gcboat · Jul 2, 2008

Re: fuel vent/smell question

The vent is usually located on the side of the boat that you fuel from. Look towards the stern, small ( usually cylindrical ) chrome fitting. Will be higher up on the side than any other fitting.

DRIFTER_016 · Jul 2, 2008

Re: fuel vent/smell question

If your boat is any thing like mine, that round cover conceals the fuel tank sender/pickup area of your fuel tank.

Indy1830SS · Jul 3, 2008

Re: fuel vent/smell question

Found the vent as described, just never paid attention to it before. Seems fine by smell.

Drifter - I have the same round cover over the gas tank. About a 4" cap in front of the engine cover. Unscrewed it and there is some gas smell from that region - not overwhelming but very noticeable and more than carb vapors. Gonna have to dig into that one as described by others above because it sounds like there should be little to no vapor smell coming from that area.

I appreciate all the comments from everyone. Thank you.

jeeperman · Jul 3, 2008

Re: fuel vent/smell question

When you put your boat under tarp next time, tape off the vent.
Then when you use the boat later and pull the cover off, the smell of gas should be zero. If the fumes are coming only from then vent.

The vent should be to an outside surface of the boat. Not into a ski-locker or any other compartment. Even if that compartment is vented.

Indy1830SS · Jul 3, 2008

Re: fuel vent/smell question

Good idea about taping off the vent, I'll try that - I found the external vent. I want to investigate the tank area as well....and might just need to take it to a pro since the confined space of tank and hoses is more than I really want to get into.

JAL51974 · Jul 3, 2008

Re: fuel vent/smell question

You could check that fuel sender unit by using some soapy water around the cover...if fumes are escaping you will see the telltale bubbles. I replaced the fuel sender unit and even with a new gasket had to go back and put a special sealant on it to really get it sealed.

Should be no fuel smell in the boat, cannot be too careful with that.

Joe

tommays · Jul 3, 2008

Re: fuel vent/smell question

You really should NOT tape the vent the tanks are only rated at about 3 PSI and very littel vacume

The volume of the tank changes a LOT from cold to hot days and you could easly suck in the tank just like a plastic gas can that was put away on a hot day and is all sucked in on the next cold day

Indy1830SS · Jul 4, 2008

Re: fuel vent/smell question

Have not taped off the vent, just left it outside the tarp.

I am convinced that there is some type of leak coming from one of the tank connections. I guess it could be the tank itself, but connections seem more likely. I now have all the connections exposed through the floor (I sure hope it isn't the tank....or I assume that whole floor has to be ripped out of there!).

So, on to the soapy water tricks I go. By fuel sender unit, do you mean the round flat connector that the fuel gauge connects to, or do you mean the fuel line to the carb? I'll need to check them all, I realize, but just curious about what you were calling the fuel sender. Also, I assume I can only get an accurate diagnosis of any leaks in the fuel line to the carb by checking it while it is running, right?

Zack

dingbat · Jul 4, 2008

Re: fuel vent/smell question

Are the original fuel, vent and fill hoses still in place? If so your hoses are probably shot and what you're smelling is the fuel permeating thru the jackets of the hoses. Fuel permeation is very common problem on boats that age that have not had the fuel system hoses replaced.

Also if you have an aluminum fuel tank it?s time to take it out for a check of its condition. Most manufacturers recommend a complete inspection and or replacement of the tank at 10 years.

Indy1830SS · Jul 4, 2008

Re: fuel vent/smell question

I've owned the boat less than a year, and am at least the 3rd owner, so I don't know for sure whether the hoses are original or not, but fully expect that they are. They appear to be in good order visually. I did the soapy water test this afternoon and found nothing.

The tank is poly, so I would think it is fine....or at least hope it is. I guess it would have never crossed my mind that something embedded in the floor, that would require complete disassembly, would ever have to be removed for inspection.....I'll keep poking around.

Zack

dingbat · Jul 5, 2008

Re: fuel vent/smell question

Unless the fuel hoses are soft and pliable they're shot.

You can't test for permeability using soap.

Plastic fuel tanks are also known to permeate over time.

How did you test the fill using soap? The fill hose was the culprit on the last two boats I diagnosed for friends.

Indy1830SS · Jul 7, 2008

Re: fuel vent/smell question

I only tested at the connections to the tank. Sponged on water and watched.

ondarvr · Jul 7, 2008

Re: fuel vent/smell question

Soap and water will only indicate a leak in a pressurized system, no pressure means no bubbles even if there is a leak.

Indy1830SS · Jul 12, 2008

Re: fuel vent/smell question

Well, I have not pressurized it and that makes sense when I think about it. Sounds like I just need to get some dealer assist on this one....not in the mood for a larger DIY project at the moment, and this one appears to be getting larger.

Thanks for all the comments and insights to folks that have responded to my questions!

Zack

fuel vent/smell question

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