gas vent leaks gas

My Sea Ray boat which has a problem with the gas vent. When I fuel the boat (and way before its full) it 'burps' gas out of the vent. It does the same when the boat warms up on a hot day. The expanding gas forces gas out of the vent - again with only a fraction of a tank of fuel in the tank. I assume that the vent hose has a low spot which collects gas during normal operation. During fueling or when the gas vapor expands, the pressure forces the liquid fuel to push up the vent hose - like a barometer would act.

Any ideas on how to fix the problem. I have thought about adding an inline fuel filter to the vent line to allow the gas to accumulate there when the pressure pushes it up the hose.

 

Sounds like the vapor recovery system is blocked up or restricted. Follow the hose which leads from the tanks fill tube.

On the side of the fill tube will be a vapor recovery hose leading the the vapor recovery system. Chances are that system is in need of service and or some type of repair.

Check all the hoses. Any one of them may be restricted and or crushed by something. Also verify the check valves are working in the system.

Engine vacuum is applied to the recovery system to purge it of collected vapors. Filling applies air pressure to one of the check valves. Another prevents liquid fuel from entering the recovery system. Anyone one of which is likely defective.

Including the vent cap on the tank and the vapor vent cap. A filter will not help. More like masking a symptom that a fix.

Search the manufacturers web site. May be a known problem. Ask the local boat repair shops and dealers. They may have a service bulletin issued on the problem or have dealt with it before.