GAS TANK - How to Empty & Clean

[cindalyn]

I've spent hours reading posts on this and other sites trying to find a SAFE, easy way to empty and clean an aluminum gas tank mounted under the floor of a 1993, 17' Boston Whaler Outrage. I see that pumping, syphoning and professional cleaning services were recommended. I'm sure I'll get a lot of comments but I'm really looking for someone that has done this in a SAFE, easy, practical way with the boat sitting on a trailer. I do not want to remove the tank from the boat or take it to a professional service.

I just purchased the used boat and the 1st owner (I'm the 3rd) disconnected the main tank and used a portable plastic tank. The 2nd owner, who I bought the boat from, thought the reason this was done is because the original owner did not want to fill a 30+ gal. tank because his boat use was only occassional and for short durations. The second owner only used the boat a few times and continued to use the portable tank.

From the fuel gauge I'm guessing that there may be 5 gal. +/_ in the tank. I have no idea of knowing how long the gas has been in the tank or if it is contaminated. I'd really like to get as much as possible out of the tank just to be safe.

My Questions:
Since there is a water seperator/filter attached am I worrying for no reason?
Should I just add some gas additive and forget cleaning the tank?
If emptying the tank is recommended - how do I do it?
If I use a pump - What kind?
Where Do I insert the hose?
If syphoning - where do I insert the hose?

Specific information/instructions would really be appreciated!

Thanks

 

[tashasdaddy]

Re: GAS TANK - How to Empty & Clean

get access to the fuel level sender, remove the sender, using a hose small enough to go thru the transom drain, siphon out the old gas. do not use an electric pump. raise the bow so all the gas goes to the opening.

 

[DJ]

Re: GAS TANK - How to Empty & Clean

My Questions:



Since there is a water seperator/filter attached am I worrying for no reason?
You do not want to use that fuel.

Should I just add some gas additive and forget cleaning the tank?
No, I would empty it.

If emptying the tank is recommended - how do I do it?
Yes, you can buy cheap siphon hand pumps from an auto parts store. I have used an old fuel hose and an outboard primer bulb. This takes a while but it works.

If I use a pump - What kind?
See above.

Where Do I insert the hose?
You should have an access plate in the deck. You may have more than one. I would remove the plate that covers the outlet fitting and use that opening. The tank outlet is usually the most aft one. The fuewl will naturally go there. While you have the fitting out, replace the anti siphon valve in the fitting.

If syphoning - where do I insert the hose?
See above. You have three possibilities. Outlet, inlet and guage opening.


Specific information/instructions would really be appreciated!

Thanks

Hope that helps.

 

[cindalyn]

Re: GAS TANK - How to Empty & Clean

tashasdaddy and DJ, thank you. I get the concept. I removed the access covers (3); the fuel sender is forward and the fill and 'outlet' hoses are aft. Based on your recommendations I'll access the the 'outlet' and raise the bow.

I assume the anti siphon valve is attached to the tank where the outlet hose attaches or is that part of the hose connector that attaches to the motor?

Thanks

 

[tashasdaddy]

Re: GAS TANK - How to Empty & Clean

if sender is forward, drop the bow so gas runs to the siphon hose. then you can mop out any crud left in the tank.

 

[DJ]

Re: GAS TANK - How to Empty & Clean

I assume the anti siphon valve is attached to the tank where the outlet hose attaches or is that part of the hose connector that attaches to the motor?

Thanks

The anti siphon valve is typically part of the outlet. If you hold the outlet fitting in your hand, you should be able to shake it and hear the valve.

Tashasdaddy has a good point. If you encounter a great deal of sludge, you may want to remove the guage/sender plate and scoop out any sludge that you cannot pump out.

Regardless, be prepared to change your filter/water seperator frequently.

 

[cindalyn]

Re: GAS TANK - How to Empty & Clean

Understood
Thanks again fellows.

 

[mattttt25]

Re: GAS TANK - How to Empty & Clean

You got all the good advice you need. Only thing I'll add is when you are done draining, fill the tank completely with fresh fuel before you're first trip out. In that way, you'll be cleaning the tank with 30 gals and the residual bad gas left in the tank will be diluted. All I'm really saying is don't drain the tank, add 5 gals and head out.

 

[cindalyn]

Re: GAS TANK - How to Empty & Clean

Make good sense. Thank you