Mercruiser 4.3L Alpha - Best way to clean gas tank?

[v1_0]

Hello,

I am working on a problem with a backfire that occurs after running at higher RPM for a while.

From some advise on this board, I am going through the fuel system from tank to fuel pump. I pulled the gas tank out of the boat (25 gal) after emptying most of the gas out - had about 2 gal left in it. Blew compressed air into the tank through both the vent and feul intake. Capped the 'fill' tube and blew air through the vent and out of the intake tube. No problems, things seemed to flow freely.

So, to be thorough, I decided to drain ALL the gas out of the tank. I did this by tipping it and letting the gas go back out the 'fill' tube into a funnel, then into a 5gal plastic gas tank. (will burn in a car, etc). The funnel happened to have a screen filter in it - and sure enough, it got clogged. So now I am sure that I have gunk in the tank.
It looks like 'bad gas' sediment. The bottom gas smelled a little funky too - hard to describe, but it seems to have a hint of 'diesel' smell to it.

Bottom line: what's the best way to clean the tank out?

Thanks,
-V

 

[a70eliminator]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

What does it look like inside? peer into it with a flashlight, remove the sending unit and pickup, hole shoud be large enough to get a pretty good look inside, it's probly all funked up with varnish and rust. I know a trick that works excellent for cleaning up rust and varnish deposits from old gas, although I haven't tried it on a large scale tank just little stuff like motorcycles and lawntractors. Anyhow here's what you do, go buy a 5lb box of drywall screws they work best because they have lots of sharp little edges, dump the whole lot of them in the tank and shake shake shake add a little kerosene too and shake till your arm is about to fall off, you can really get the tank clean inside, I did a cycle tank that was just rusty as all get out and it came out shiny inside useing the screw shake technique.
Ok I know it sounds hoakey but ........ what do have to loose?

 

[JustJason]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

Drywall screws???? you can't be serious.

 

[a70eliminator]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

I knew I was about to be the laughing stock of the day, but went ahead and posted it anyhow. Someone showed me years ago on an old motorcyle gas tank and I've been a believer ever since, done it several times on little 2-3 gallon tanks it works great, just never on a large 20gal tank. Drywall screws are the best as I said thety have lots of sharp edges thet cut the crud.

 

[Don S]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

Moving to Boat Topics and Questions (Not engine topics)

 

[v1_0]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

a70eliminator,

I've done that with motorcycle tanks too - then put in some "kreem" to seal them up real good. It isn't stock, I know, but then I was interested in riding and not in collecting.

At any rate, the boat's tank is some sort of plastic - so I wouldn't think that sharp metal things are the way to go on this one..

But you have given me an idea - I could pull the sender and use some sort of bottle brush (I have one for a 5 gallon glass fermenter that I used to make beer with long ago...) The brush is nylon, so it shouldn't hurt things. Better still, I could strap one of those nylon 'brillo pad' like things to a stick and run it around the bottom of the tank.

The tank didn't really seem all that bad - there were just enough flakes to clog the filter up some (they looked like fishfood flakes) but not much more than that.

One question: when I put the sender back on, do I need to replace a gasket or something?

Thanks,
-V

 

[mkast]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

Look in the yellow pages for a radiator place. A lot of them clean gas tanks. It's a lot safer and the tank will be spotless when you get it back.

 

[Cptkid570]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

With the "shake shake" method with the drywall screws, I'd think that you would have to be carefull not to just dump a box of them in there because the box may have some metal shavings/chips in there and you don't want those getting left in the tank.

Interesting concept though..

However, as mkast said, take it to a radiator shop..they could probably do it. The easy part is that you have the tank out and can actually hold it in your hand and dump it from side to side.

You could maybe just dump some really good fuel cleaner in there and let it sit.

 

[JustJason]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

how big a gas tank we talking about here? and is it permantly installed in the boat or is it removeable?

 

[180shabah]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

how big a gas tank we talking about here? and is it permantly installed in the boat or is it removeable?

per the original post

I pulled the gas tank out of the boat (25 gal) after emptying most of the gas out - had about 2 gal left in it.

 

[Hvymtl]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

go buy a 5lb box of drywall screws they work best because they have lots of sharp little edges, dump the whole lot of them in the tank and shake shake shake add a little kerosene too and shake till your arm is about to fall off,

We were to poor to buy screws...just used pea gravel instead

 

[Vegas Naturist]

Re: Mercruiser 4.3L Alpha - Best way to clean gas tank?

Drywall screws???? you can't be serious.

Never heard of using drywall screws, but... I had a friend who was restoring a 1949 Hudson Commodore, and the fuel tank was very rusted inside. He dumped a bunch of sand and gravel in the tank, strapped it to a cement mixer, and let it turn for several hours. Tank was sparkling clean inside! Picture it for a good chuckle, but it worked...

John