Fuel Tank Cleaning

[kcm805]

This summer I picked up a 1979 Glasply 19ft runabout for a pretty good price. Needed a few things but got it running and had a blast on it. Previous owner said he had no idea the condition of the main tank so I just ran it off some gas cans. Now that it's winter, I pulled the 50gal aluminum tank out and to my surprise it was mostly empty. Looking through the pickup tube and the fuel sender hole I can see no corrosion inside and it's mostly clean except for some loose dirt/dust and maybe 1/4 gallon of varnished gas/oil mix. What is the best way to clean this out? Simple green and water then run a fan into it for a while to dry out? Exterior however has some corrosion and pitting on the bottom (see pics). Its a little hard to see in the pictures but in some of those small brown/white spots there is a layer of metal missing. Kinda like rust on steel and it flakes away. The pitting does not go all the way though the tank (visually at least, no idea if there is a small pinhole). I am planning to pressure test the tank to check for leaks but i am a little worried about future ones developing too due to the pitting. Is it possible to seal it from the outside? I was thinking about using epoxy paint or is something else better for this? Or maybe its not even safe to reuse this tank? Thanks for any advice as I am kinda new to this.

 

[Chris1956]

As you suspect, aluminum tanks to develop pinhole leaks. You should pressure test it to make sure it doesn't leak, before doing anything with it.

Put a couple of PSI into it and spray it with soapy water to check for leaks.

I do not know of a way to fix it if it has leaks. I used marine-tex and fiberglass cloth to repair a steel fuel tank, but whenever it flexed, the patch broke. I presume your tank would do the same.

 

[tpenfield]

Corrosion should be your main concern. I would assume that the tank is 0.125" thick aluminum . . . so the corrosion can lead to pinholes or at least very thin areas of the tank (1/16th inch ).

You may find that you need a new tank.

How does the structure of the boat look, now that you've pulled the tank?

 

[mike_i]

I agree with the other guys, i'd get it pressure tested before doing anything. If you need to replace it I would'nt worry about the new tank corroding, most likely you'll be long gone before that happens beside you can also get a custom made plastic tank. Was the tank foamed in?

 

[kcm805]

There is no foam or wood down there. Its all fiberglass on these earlier Glasply boats. Its in good shape too. All solid feeling and sounding. I think your right about how thin the material has gotten in those spots. Measured a few and they are 1/16" or so depth of material missing.

 

[Scott Danforth]

cut-n-pasting from past threads:

Here is what I have done in the past
simple cleaning - 2 gallons of simple green, followed by 2 gallons of boiling hot water, go for a drive down a back country gravel road at 40mph - drain
removal of fuel deposits - 3-4 gallons of denatured alcohol followed by the drive down a back country gravel road at 40mph
removal of rust - fill tank half full with vinegar (or 20:1 mix of water and muriatic acid), let sit for a week, go down the same gravel road. drain. then fill tank with hot water and soda ash to neutralize the acid content. http://www.galvatech2000.com/documents/docpdf/NEUTRALIZATION_OF_ACIDS_eng.pdf
after rinse, repeat the simple cleaning method above and then run a gallon of isopropyl alcohol into the tank take the same drive, then drain.

also suggest pressure testing your tank.

 

[Grub54891]

That pitting looks serious. I think it best to replace, you have the perfect pattern, possibly someone local could fab one up or send it out to get a duplicate made out of aluminum or plastic .

 

[kcm805]

Pressure tested tonight. No leaks at first however I saw a corroded spot that looked worse than the others I missed before. Was scraping to clean the dirt/loose corrosion off to measure the depth and poked right through. Dept of the corrosion was .080" in the surrounding area. Found and cleaned up the label on the tank and it was originally .090" thick. Many spots are .060-.070" deep. It's done. No way I trust this. Thanks for the advice.

 

[Chris1956]

There are lots of standard fuel tanks on the web. Measure the size of the cavity in the hull and see if you can find one that is pretty close to the original size. Then look for a sale price on it.

If that fails, you can always get a custom one fabricated for lots more $$.

 

[redfishsc]

You have a nice 50 gallon raised bed garden. Maybe two 25 gallon planters if you're reasonably skilled with a jigsaw.

50 gallons is a lot of gasoline to have leaking in your boat. I know new tanks aren't cheap but it's way cheaper than a bigass boat & garage fire.

 

[76SeaRay]

My aluminum tank was a 1976. Even the fuel sender was corroded off and in the bottom of the tank. I had a new custom tank made for mine, 60 gallon made to the same size and fit as a drop in replacement, $825.00 (price is a year old).