Gas smell coming from gas caps

[JimCarver]

Hello,

A few hours after shutting off the engines on our '04 Mariner 360 with 6 liter Crusaders gas engines, a slight gas smell comes out of our gas caps. We dos have the full canvas enclosure on the rear part of the boat (see pictures) and that doesn't help, but still, is this normal? Since the smell goes away a few hours after the engines have shut off, I deduct that the heat from the engines is bringing the smell up to the caps.

Also, I kneel down and put my nose all around the engine area and the smell is definitely not coming from the engine room and only from the gas caps.

Thanks for your time giving me your opinion on this.

[Midnightsun]

That filler happens to be the same filler as mine. Could not find my tank vent so I started researching on where it could be. Found out they are built into the cap assembly! Bottom line is venting occurs at the cap so smelling some fumes there would be normal. See picture on the link. https://www.asap-supplies.com/products/ ... ent-305587

Get asked quite often on where my vent is located when fuelling, not many know about vented caps.

[km1125]

QR_BBPOST That filler happens to be the same filler as mine. Could not find my tank vent so I started researching on where it could be. Found out they are built into the cap assembly! Bottom line is venting occurs at the cap so smelling some fumes there would be normal. See picture on the link. https://www.asap-supplies.com/products/ ... ent-305587

Get asked quite often on where my vent is located when fueling, not many know about vented caps.

Wow. I'm surprised to learn that they built some that way. If you look at the OP's boat with the canvas, those fumes end up inside the boat. Even if he didn't have canvas, then a slight breeze could/would also bring those fumes into the boat. I wonder how they handle the loop in the vent line? That's typically designed to trap any water that might get into the vent and allow it to drain overboard. Can't see how that could happen on an installation like the OP's.

[Midnightsun]

I wonder how they handle the loop in the vent line? That's typically designed to trap any water that might get into the vent and allow it to drain overboard.

You do not need a loop on these as water cannot get in like a typical hull mounted vent. Perko makes several styles incorporated into the filler cap like above. The other advantage is when the tank is full and the vent wants to expel, it does so on the fuel nozzle (returns to tank) which turns it off just like as if the tank was full so no vent spills in the water.

I have never smelled fumes on mine however I do have diesel so maybe not as noticeable? I also have a custom enclosure where the aux tank fillers are enclosed very similar to the OP.

[Viper]

Ya that design has been around for a while, I'm not that crazy about them though as they limit your options IMO, and as mentioned, I don't like the possibility of fumes venting inboard. As far as I'm concerned, the only way they should be mounted is overboard on a vertical surface, this solves the venting issue and gives you options with vent hose routing for creating a loop. That's the way I'm used to seeing that type of design installed.

[JimCarver]

Thanks for taking the time to share guys.

So what do you suggest I do to eliminate the gas smells possibly creating fumes? The seals inside seem in great condition.

What is OP by the way?

[Midnightsun]

You are the OP. (Original Poster) The seal only seals the filler so to say and not the vent. If the vent were to be sealed it would not be a vent anymore. The only fix I can see is to remove the vent line attached to the filler port and relocate using a standard hull type vent.

[bud37]

QR_BBPOST Hello,

A few hours after shutting off the engines on our '04 Mariner 360 with 6 liter Crusaders gas engines, a slight gas smell comes out of our gas caps. We dos have the full canvas enclosure on the rear part of the boat (see pictures) and that doesn't help, but still, is this normal? Since the smell goes away a few hours after the engines have shut off, I deduct that the heat from the engines is bringing the smell up to the caps.

Also, I kneel down and put my nose all around the engine area and the smell is definitely not coming from the engine room and only from the gas caps.

Thanks for your time giving me your opinion on this.

Have your canvas guy adjust the side curtain to go inboard of the vent/fill.....it should be that way anyway. I am sure if you show him/her the problem a solution can be met......good luck and keep that side curtain off that area until it gets looked at.

There will be an issue with water drainage but choose the lesser of the evils.......these people can be quite creative.

[Viper]

Ya the canvas person can modify the enclosure there to go on the inboard side.

QR_BBPOST..... The only fix I can see is to remove the vent line attached to the filler port and relocate using a standard hull type vent.

You can only do that if you cap off the vent port on the deck fitting otherwise you run the risk of overflowing fuel into your bilge.

[JimCarver]

Hey guys, thank you for taking the time for your comments and suggestions, I really appreciate it. And now I know what OP means!
I think the simplest option is to modify the canvas while finding a way to reroute the rain water away from inside the boat. Like you say, canvas people can get creative sometimes. And a bit of water is better than a lot of fire! If I don't like sometimes getting wet, I'll just stay home, and that won't happen.
Have a sweet Sunday!