Re: How to drain old gas from on board tank
Here is how i did the one i needed to drain. Use a air compressor and put pressure in the vent line from the tank with the fuel line off of the engine . The pressure in the tank will make the fuel come out the line you took of of the engine. Hope this helps.
be VERY VERY cautious here.... as little as 3 psi or less can damage a fuel tank (which COULD even have deadly consequences)....... I'm not saying it CAN'T be done but this is a risky endeavor.
example fuel tank measures 20"x40"x 6" .... On the 20"x40" surface there are 800 square inches and a 3 psi (pounds per square inch) you have 2400 lbs of pressure acting on just that one surface. Add that to the pressures on all of the surfaces and you can see there is a huge destructive force....
Be aware to that there is likely to be an anti siphon valve in the fuel pickup which would make siphoning impossible.... If you have access to the tank you can usually unscrew the pickup and insert a fuel hose through that hole to siphon fuel.... Then run that hose through the bilge drain
Also there is usually a valve in the fuel fitting that connects to an outboard to stop fuel from flowing when not connected to the motor.
