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Fuel smell only when tank is full

Posted: Sat Jul 05, 2025 10:18 am
by Bmcs22
Recently purchased a ‘17 R5 and love it.
When I fill the gas tank up full, there is a very strong gas odor. Doesn’t seem to be in the engine compartment but is really strong around the fuel tank. I’ve tightened all the hose clamps, sending unit and fuel pick ups but still have the gas odor.
It has these 2 plugs and not sure what they are. There seems to be gas on them when I touch them so I’m wondering if the gas can be seeping up through them. There is also what looks like a thin layer of gas on the top of the tank- not much but it doesn’t take much. I’ve tightened them also but I’m wondering if there are gaskets or o-rings that can be replaced. I don’t want to take them out without knowing what would happen if I remove them to seal them better.

Anyone else have this problem and what did you do to solve it.

Re: Fuel smell only when tank is full

Posted: Sat Jul 05, 2025 2:06 pm
by bruceb58
I get the same on my 2017 R5. My guess it's that charcoal canister. I make sure I use the blower and its gone after driving the boat for a mile or so.

Re: Fuel smell only when tank is full

Posted: Sun Jul 06, 2025 5:42 pm
by drtbar
Bmcs22 wrote: Sat Jul 05, 2025 10:18 am Recently purchased a ‘17 R5 and love it.
When I fill the gas tank up full, there is a very strong gas odor. Doesn’t seem to be in the engine compartment but is really strong around the fuel tank. I’ve tightened all the hose clamps, sending unit and fuel pick ups but still have the gas odor.
It has these 2 plugs and not sure what they are. There seems to be gas on them when I touch them so I’m wondering if the gas can be seeping up through them. There is also what looks like a thin layer of gas on the top of the tank- not much but it doesn’t take much. I’ve tightened them also but I’m wondering if there are gaskets or o-rings that can be replaced. I don’t want to take them out without knowing what would happen if I remove them to seal them better.

Anyone else have this problem and what did you do to solve it.
Post some pics of the plugs you're talking about

Re: Fuel smell only when tank is full

Posted: Sun Jul 06, 2025 8:00 pm
by billk2632
You do not want to overfill the tanks on these boats by topping off. Doing this will cause gas to overflow into the charcoal cannister saturating it with fuel. Not saying you did this, but if someone did it will mess up the charcoal filter and cause smells. Those two plugs you are referring to are probably part of the charcoal cannister / vent system, might need to replace the gaskets on them - it is strange they would be leaking unless it was a problem from new. If you have a manual for your boat there will be a section about the fuel system with diagrams. You can download them from the Cobalt site. I would get to the root of this and resolve it -- it does not take much fuel to cause a big problem.

Re: Fuel smell only when tank is full

Posted: Fri Jul 11, 2025 1:56 pm
by Bmcs22
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