Chaparral will not fill up gas tank, overflows

[muley101]

I have a Chaparral 185 XL. When I try to fill the tank, the line going to the tank fills up and immediately overflows from the gas cap hole. I have checked the air vent and it is not blocked. I took the cover off the top of the tank and I can hear a trickle of gas going into the tank. It appears that the pipe to the gas tank is blocked. Is there an anti siphon valve that could be blocked? Any other ideas? It looks like I would have to take the floor out to replace the gas tank fill pipe, so not an option. Also, I tried to run an electrical snake down the filler pipe and it only goes about 3 feet before it stops, also making me think there is a blockage. This is driving me nuts because I can't put gas in the boat.

 

[Scott Danforth]

I would start by removing the fill hose and inspecting. The fill hose on the tank is most likely an inch and half diameter. If the hose deteriorated the inside wall could be closing off. You could have some other blockage. However before you go jambing stuff down the hose, remove it and inspect.

If you need to replace the hose, make sure You are using marine rates fuel fill hose

 

[Old Ironmaker]

How do you know for 100% the vent isn't plugged. I had the exact same thing happen on my 19 foot StarCraft. I was sure the vent was clear as I ran a heavy gauge wire down it. I was not about to rip the floor out and it took me a good 15 minutes to fill the tank from 3/4's. A bit of gas let it gurgle down, a bit more and repeat. Then I got a brain storm. I took the vent cap off and taped the hose from the compressor on it, left the cap ON and gave it a few shots of air. Then I heard the fuel move in the tank. Took the hose off and watched fuel spill out. With the cap off and towels on the gunnel gave it a shot of air and gas came out the filler. Problem solved. I thought 100% my vent was clear too. I'm told it may have been a vapour lock that I cleared. I'm not sure of the dynamics of vapour lock. Now as a PM I give the vent a shot of air when topping up tires when the boat is home.

Give her a shot of air before you get into a huge job.

 

[Scott Danforth]

Be careful. Above 5psi will damage the tank.

 

[GA_Boater]

Be careful. Above 5psi will damage the tank.

Yep! I would only blow the vent with the filler cap open. With some protection, too. Gas in your eyes does not feel so good.

 

[Watermann]

There should be no restriction in the filler line maybe it was only a turn you ran up against with the snake.What year is the boat? How did you determine the vent was clear? Some manufacturers put a one way valve in the vent line and the check ball inside can get stuck not allowing anything to pass through either way.

Look for something like this in your vent line. Here's the link to it. Boat Fuel Vent Line Surge Protector