Smell Gas But Cant Find The Source

[Reefdog]

Hello Cruisers,

I have a 1986 20 Ft Grady White that has started to smell strong of gas fumes when I get up on a plane. I do not have any gas in the bilge and have fixed the seal around the sender on the gas tank but still smell it. Does anyone have any tricks for locating where the fumes may be coming from or any suggestions of a place to look?
Just to recap
No gas in bilge
No leaks from hoses
No gas seen in the water
Thanks

[Kettlewell]

Stop using the boat and figure it out! Is it inboard or outboard powered? Check the breather line to the gas tank both where it attaches to the tank and where it goes overboard. Check the gas fill cap is sealing tight. That boat is old enough so the hoses may or may not have been ethanol proof, and should have been replaced by now.

[skipmac]

Pay very close attention to Kettlewell's advise. He knows the subject.

But to second the advise, do not use this boat until you find the leak. Gas fumes can explode violently.

Check all hoses:

1. Fill lines to the tank
2. tank vents
3. line from tank to engine
4. all over the engine, any shorter lines, etc

Pay particular attention to the ends of all these lines where they connect to fittings and barbs. Sometimes old hoses will have hairline cracks that aren't easy to see. Try bending and flexing the hoses to see if any small cracks open up. If the hoses are hard, stiff and inflexible probably a good idea to go ahead and replace them.

Be careful.

[Reefdog]

Thanks guys,
I have checked all the hoses and they seem ok. If they are bad I would see gas coming out right? I may have to hire some one.

[never monday]

sterndrive, inboard, outboard?
how old?
what engine?

[Kettlewell]

I have found that when they switch over from summer to winter gas, or winter to summer gas, my nose picks up the different odor and I wonder if I've got a leak. Ethanol gas has a pretty strong odor that is different too. What type of engine are we talking about? If carburetors your float might be sticking or something else could be wrong causing your engine to run rich, which you can often smell.

[HopCar]

"strong of gas fumes when I get up on a plane"

Do you only smell it when the boat is on a plane? That seems odd but I'm not sure what it could mean. Maybe a small weep in the aft end of the tank near the top?

[svHyLyte]

Originally Posted by Reefdog

Hello Cruisers,

I have a 1986 20 Ft Grady White that has started to smell strong of gas fumes when I get up on a plane. I do not have any gas in the bilge and have fixed the seal around the sender on the gas tank but still smell it. Does anyone have any tricks for locating where the fumes may be coming from or any suggestions of a place to look?
Just to recap
No gas in bilge
No leaks from hoses
No gas seen in the water
Thanks

Depending upon the configuartion of your boat, you maybe experiencing a "pickup truck tailgate effect" coupled with somewhat incomplete combustion of your fuel. With a center console type boat with a large wind screen and low aft-deck, at speed a relatively low pressure area extends from the aft end of the console toward the transome. This can have the effect of creating a counter airflow up and over the transome and back into the aft deck area. If, in fact, your exhaust includes hot but unburned fuel (along with other fumes), the smell could be pretty strong. At lower speeds, the effect doesn't develop. I have seen the foregoing effect on other motor boats.

Just a thought...

[skipmac]

Originally Posted by Reefdog

Thanks guys,
I have checked all the hoses and they seem ok. If they are bad I would see gas coming out right? I may have to hire some one.

Well, the leak could be hard to see. Have you inspected the entire hose, espeically both ends but the whole length as well, especially anywhere the hose bends around a bulkhead or goes through or around something that could chafe a hole?

Is the smell only when you are getting on plane or the whole time you are on plane?

If only when getting on plane or a lot worse getting on plane think about the angle. The bow rises and the acceleration moves all the gas to the back of the tanks.

[Reefdog]

Wow thanks for all the advise. The engine is a 2002 Yamaha 150 four stroke out board and it runs very well. I do have the air flow pattern svHylyte mentioned so it could be that but its is more so than normal. I noticed the problem when I took my deck hatch off over the gas tank to get fixed. I took a few trips with the hatch off and noticed that the boat really smelled like gas. I found that the sender cap gasket and the metal around it on the tank was pitted and have since capped it with new aluminum plate and marine text. I know I should have used a gasket but we didn't. The smell has gotten much better but does still come up when I get on a plane. Through out the whole process of locating the source of the smell there has been no gas in the bilge. I just tried washing the tank and the hoses and bilge area to get any old gas off.

[never monday]

have you pulled the engine cowling to look for fuel leaks?

[skipmac]

How is the tank mounted? I had a Wellcraft years ago with an aluminum gas tank that was foamed in place. Over time moisture will collect in the foam around the tank and corrode tiny, pinholes in the bottom. Hard to see and not enough to leak a lot of liquid out. Gas especially is tricky because it has such a high vapor pressure (it evaporates really fast) so small amounts of liquid gas quickly turn into vapor, which is worse because the vapor is very explosive.

Look at the photos on this thread. http://www.cruisersforum.com/forums/...ank-99398.html

These leaks are on the inside of the tank and not from the same cause but it gives you an idea of what can happen with aluminum tanks over time.

[Richard_W]

I do not know that engine and suspect that what I am going to say is not applicable to this (smaller?) engine, but here it is ...

If you have 8 cylinder, or even 6 cylinder engine, and one of the spark plugs goes bad, you might not feel it right away but you might smell it ... the unburnt gasoline fumes in the exhaust gases. If that is a carburated engine, it might also require a tune-up ... gasoline/air mix too rich.

As mentioned above, be careful with gasoline fumes. Take extra care of venting the engine/tank compartment (use diligently blowers if you have them) before you start the engine and at idle speed, and look for the leaks on the outboard after stopping the hot engine.

[DeepFrz]

I would suggest that if you had pitting and leaking on the top of your tank that you probably have pitting and leaking elsewhere on the tank. I think its time for a complete tank inspection. Be careful...

[Reefdog]

Thanks everyone, I think it is going to be a combo of the gas not sully burring and the tank and hoses needing to be replaced. I am going to have a pro look at it this week. Thanks