Fuel vent issues 4.5L 250hp Mercruiser

[Jnels11]

When I try to fill up my 2018 Chaparral 21 H2O with a 4.5L 250hp Mercruiser I have to fill it up super slow as the back pressure trips the pump handle. It’s to the point that I have to let the fuel trickle in. Has anyone had this issue? I have read others having issues with a vent tube my vent tube connects to some kind of canister. My thought is that this is a charcoal filter of some kind but have not seen one on a boat before was not able to find much about it online. Could this filter be the cause of my issue? Anyone with this setup have a similar issue and how did you remedy the issue?

 

[alldodge]

While those things can cause issues, it's more then likely how the hoses were run, or the size of the fill hose.

Look at the fill and vent lines paying close attention to how they route from tank to fill/vent

https://www.boats.com/on-the-water/modern-gasoline-fuel-systems-on-boats/

 

[Fun Times]

Looking up the part number of the EPA Certified Carbon Canister that meets EPA diurnal emission control requirements shows it's an Atwood Marine product... Inside the link at the top there looks like an installation guide you could try downloading as maybe it will help show if it's installed correctly, etc...

Attwood Marine

Attwood Marine offers a broad range of boating and marine accessories. Visit us to find info for EPA Certified Carbon Canisters and to find out where to buy.

old.attwoodmarine.com

 

[ROY WILLIAMS]

the canister is to remove it and then put some air in it and the canister is blocked up flow .. or the canister is the air filter vent or the hose is distorted
use the air pressure ....

I did my old vehicles and the gas has a gas pump valve on the gas station ...
my gm truck had the vent valve to replace it ..

canister is around 140 bucks

 

[tank1949]

When I try to fill up my 2018 Chaparral 21 H2O with a 4.5L 250hp Mercruiser I have to fill it up super slow as the back pressure trips the pump handle. It’s to the point that I have to let the fuel trickle in. Has anyone had this issue? I have read others having issues with a vent tube my vent tube connects to some kind of canister. My thought is that this is a charcoal filter of some kind but have not seen one on a boat before was not able to find much about it online. Could this filter be the cause of my issue? Anyone with this setup have a similar issue and how did you remedy the issue?

REMOVE CANISTER AND TRY BLOWING THROUGH HOSE. Mud Dobers are bad here about plugging air vents. The screens might need replacing too.

 

[QBhoy]

Think this is quite a common issue. Or it has been for me with any North American boat I’ve had. Often had a blast of fuel in the face as a result. Found it best to start off slowly and find a nozzle position that doesn’t try and seal the fill hole by only sticking the nozzle in a little of the way.

 

[Jnels11]

Looking up the part number of the EPA Certified Carbon Canister that meets EPA diurnal emission control requirements shows it's an Atwood Marine product... Inside the link at the top there looks like an installation guide you could try downloading as maybe it will help show if it's installed correctly, etc...

Attwood Marine

Attwood Marine offers a broad range of boating and marine accessories. Visit us to find info for EPA Certified Carbon Canisters and to find out where to buy.

old.attwoodmarine.com

Thank you for sending this over. I believe mine was mounted where the hose from the tank is on the high side and the hose to the p-trap is on the low side (opposite of instructions). Might have to mess around with it and also make sure lines aren’t plugged.

 

[Jnels11]

REMOVE CANISTER AND TRY BLOWING THROUGH HOSE. Mud Dobers are bad here about plugging air vents. The screens might need replacing too.

I hate those things and they are bad. I’ll have to take it apart and see

 

[Jnels11]

Think this is quite a common issue. Or it has been for me with any North American boat I’ve had. Often had a blast of fuel in the face as a result. Found it best to start off slowly and find a nozzle position that doesn’t try and seal the fill hole by only sticking the nozzle in a little of the way.

I even tried that and still nothing. I think it took close to 20 minutes to get 20 gallons of gas in it. Needless to say I was not a happy camper….

 

[ROY WILLIAMS]

I even tried that and still nothing. I think it took close to 20 minutes to get 20 gallons of gas in it. Needless to say I was not a happy camper….

the boat mechanic to have to inspect the fuel tank items ...
you put the gasoline in the tank and it is a very low amount ..fix it ..

 

[Lou C]

Something isn’t right there my brother has a 2020 Chapparal 21SSI with the same engine & does not have that problem….

 

[flashback]

I routinely clear mud daubers out of the tank vent.

 

[Dubed]

Maybe a dip in your vent line that acts like a p-trap. My buddies boat has this issue. He simply puts a tube in or over the vent and blows the vent line clear before fueling. Solved his problem

 

[Jnels11]

I forgot to update this thread but the canister was the problem. It was plugged up so I ordered a new one and now the boat fills up as it should!! I appreciate all the feedback and suggestions!!