356 aux gas tank/ Need to siphone old gas out?

[ozarkboater]

I have owned this 356 for two years now. The old owners owned the boat for five years and told me they never used the aux tank in the rear. That's seven years the aux tank has not been used. The fuel gauge reads less than 1/4 tank. I talked to the original owner of the boat and he told me he used it all the time. Wanted to insure myself nothing was wrong with the tank before I got too carried away.
I want to siphon every bit of fuel out of the tank before I use it. The boat is in the water of course, so the tank is lower than where I will be siphoning from. I was wondering if any one had an idea of the best way to go about this? By the spec sheet there is 7 ft. of hose from filler cap in the rear of boat to the tank. Or should I be thinking of the opposite direction and try to drain it from the fuel line at the supply valves, and how would I go about this?

Any help or ideas would be appreciated... Bill

[mjk1040]

Well you can get most of the fuel out thru the aux. supply line to the control valves. The back wall of the back berth should come apart to allow you access to the aux. fuel tank. Have you thought of trying to pump it out from the filler port? Long enough clear hose on a vacuum extractor?

[Viper]

You'll only get so much pumping it out though the existing pick up tubes as they don't go all the way to the bottom. I did this very thing by accessing the tank through the aft cabin and extracting through the sender port.

[ozarkboater]

Well, I think I would rather extract it out through the filler tube. It would be a lot less work the tearing the bed and wall apart. And if I understand you both, it's the only way to get to the bottom of the tank? What to use ? would a shop-vac have enough suction for seven feet of tube and would it be safe? or is there something specific I should use?

thanks Bill

[mjk1040]

Don't use a shop vac. greater chance of an explosion or fire. Buy or borrow an oil vacuum extractor. It'll take sometime at 6 or 7 quarts at a time. Or and explosion proof extraction suction pump. Be Safe. If you don't mind sharing, what did the Sea Deck set u back?

[Viper]

Source of the post Don't use a shop vac. greater chance of an explosion or fire. Buy or borrow an oil vacuum extractor. It'll take sometime at 6 or 7 quarts at a time. Or and explosion proof extraction suction pump.....

++1
You can also rig up an electric fuel pump with some fuel line.

[km1125]

Really, to do it right you need to go through the sensor.

You can buy a low cost fuel pump and pump most of it out via the aux line... that would be fairly easy. But it would only get you to the low end of the pickup tube. Also, if you know which end of the tank the pickup tube is on, you can list the boat to get even more out.

Then, take the berth apart and get to the sensor opening and use the pump again with a hose that goes to the bottom of the tank. I put a low-cost in-line filter in before the pump just so you don't suck any debris into it an ruin it early in the process.

This two-step process would minimize the amount of time you'd have to have the berth taken apart.