Question For The Boat Guys, Gas Siphoning Thru Carb.

[jdmidwest]

I came home today to find that my new to me boat had pumped out the gas tank thru the carb. The motor was tilted on the transom saver and the gas had run out of the front, filled the transom wells and overflowed out on the ground.

I unhooked the gas line and cleaned the mess up, but wonder how it happened. It is an 88 Merc 35hp with a carb and a metal 6 gal red gas tank. Did the heat of expansion cause the gas to flow or is something else going on? I am trying to figure out how it run uphill about 2 feet.

[gotmuddy]

check the gas tank vent, probably stopped up

[fishinwrench]

Yep. Pressure built up in your fuel tank. Check the vent.

On the old metal tanks you vent by loosening the cap 1/4 turn.

[jdmidwest]

I thought you only loosen the vent for running and close it for storage and travel. Vent was closed.

[fishinwrench]

I thought you only loosen the vent for running and close it for storage and travel. Vent was closed.

Correct, but you need to disconnect the fuel line if it's not vented.

I prefer caps with an adjustable thumb screw vent and I never tighten it all the way, because if you ever connect the fuel line before relieving pressure you risk getting sprayed in the face.

[jdmidwest]

I took the day off and was installing new AC on the house. I had the boat open and drying out. The bunk with the batteries and gas tank was pretty hot there sitting in the sun. Tank is vented and hose disconnected while parked now.

The bunk hatch was open and it was like an oven in there. At least I know all my lines are good and pressurized.

Last guy had the boat setting outside in the weather for at least a few weeks since I spotted it. Lots of rain had it soaked good. Another nice day of sun it should all be dry.