Below Deck fuel tank replacement?

[bennnyjw]

Hello,
I recently purchased a 1993 sunbird corsair 170 with outboard and below deck 23 gal tank.
I have had fuel issues and bought a new fuel sender and pick up tube, both of the old ones were covered in grime/scale.
I cut in an access hatch in order to replace those parts as I only had a small round hatch before.
I have plenty of tools and some experience in woodworking and work on hvac equipment for my trade.

But... I made a drastic mistake by thinking I had a jug of coil cleaner to use on the top of the tank, but it turned out to be vinegar ............... Which obviously created a few pits in the tank, and one near the feeder that went all the way through.

My main question is can I repair these pits and the hole? Or do I make the even more time consuming job or cutting out the tank completely? I am also unsure if the vinegar made its way to places I cannot see? Pressure test the tank? The tank manufacturer RDS told me the tank is about 25x45x5 which makes it a good portion of the floor space of my boat and where I would probably have to remove my double seats on each side.

I was also planning on using pvc trim board to replace the existing part I cut out, either making it a hatch, or sealing it in and possibly carpeting over it something.

If I cut the whole tank out I would like to use pvc for that too, but realize I may need to secure it and seal it good for rigidity and moisture?

Thank you!

 

[alldodge]

What is the tank made out of?

I'm not seeing vinegar eat thru a tank even in long term. If its aluminum I see water is what did the damage and the vinegar just cleared away the corrosion. Seeing replace the tank is the way to go.

If the tank is foamed in, I'm would foam it back in, but coat the tank real good with epoxy

 

[kcassells]

Yup, I concur with Mr.ALLDOGE.The vinegar cleaned off the crumbola and exposed rather serious problems that
would have ended up anyway to be addressed.
As far as foaming it back in there are a number of opinions that you can research. I guess the first issue is how to get the tank out without doing to much damage. Post some pics when you can. Looks like RDS makes custom aluminum tanks.

 

[bennnyjw]

I just always remember hearing about not letting vinegar get on aluminum.

I have reached out to rds about a replacement, quoted about $480. Id prefer not to spend that much. I do kind of like the idea of plastic for a replacement. And might be cheaper than another aluminum?

The black stuff is jb weld tank seal I hoped would sure up the hole and divots.

if I can replace the floor I cut up with PVC boat it should be a much easier project?

 

[alldodge]

Don't understand replacing the floor with PVC, but if you can I'm sure that will be fine. You can have a plastic tank made, and should be less then aluminum, but will probably be a few less gallons, due to plastic being thicker.

I replaced my water tank with a guy out of TX which took sheets of plastic and welded them together

 

[kcassells]

Good luck says I.

 

[tpenfield]

If you have holes and pits in an aluminum tank, it probably looks worse down below. It would be best to take the tank out. Don't worry about how to patch up the hole. That may be the least of your problems once you get a look with the tank out of the boat.

 

[bennnyjw]

If you have holes and pits in an aluminum tank, it probably looks worse down below. It would be best to take the tank out. Don't worry about how to patch up the hole. That may be the least of your problems once you get a look with the tank out of the boat.

I guess I will see, Doesent seem to be any soft spots in the floor, the parts I cut up so far we’re well epoxied and dry. Hopefully not a nightmare.

 

[bennnyjw]

I am also striking out trying to find a tank to fit as a replacement besides an exact match from rds for almost $500.
Any ideas? 45x26-1/2x5
thanks

 

[kcassells]

Craigslist and ebay may come up with something.

 

[alldodge]

The place where the tank takes the hardest hit is on the very bottom, if water/moisture is present. The water will eat thru an aluminum tank, just tanks a while

 

[bennnyjw]

Thanks for the replies!

Got the floor up, tank is dirty at the top, but seems like the vinegar is definitely what pitted the tank.
problem now is tank feels like it may be glued in? Hopefully just a little stuck from years of sitting. Any tricks to get it out?

 

[kcassells]

No pics no work....no believe.

 

[alldodge]

If there is foam around the tank, it needs to be cut loose from around it

 

[bennnyjw]

No foam that I can see, going to try a hand saw blade tomorrow and wiggle it.

 

[MTboatguy]

Well right now, all I can say is you have a bit of a mess on your hands. You need to get that tank out, it is not a salvageable tank, so if you have to cut it up to get it out, then access any damage that is below it or on the sides, normally a tank is not the only damage. The vinegar did not eat through the tank, it simply removed the corrosion that was already there and welded to the tank, But first things first, get the tank out in the easiest method you can figure out, you are into to it now, so fix it properly so you don't have to do it again a few years now the road, To be real honest with you and having boats of that vintage before, I would be a bit concerned about stringers and the transom and would be poking around to see what is going on with them.

Good luck, we are here with support and information,but again at this point you are into it and it should not be short cutted to fix it.

Look at the moeller website, they should have a below deck plastic tank that will fit that space, might hold more or it might hold less but it will be designed for this type of situation.

 

[tpenfield]

I would not do any sort of cutting of a metal fuel tank for fear of sparks and ka-boom

Figure out what is holding the tank in and go that route. some are foamed in and some are fastened in. You should be able to sort this out.

 

[MTboatguy]

Aluminum and steel hand saw blades don't create sparks in the environment we are discussing, as there are no straps around that tank, I suspect it either has foam that is hidden holding it down, or there are swollen stringers on either side of it that are holding it down. That said, if it don't have straps, you should be able to get something under the bottom of the tank and pry it out.

Now aluminum powder in the right environment can be explosive, but a hacksaw is not going to create that environment to create aluminum dust that would explode, this would not be considered hot work.

In our gun business we use steel bits to machine aluminum every day and it does not create a fire hazard. For the most part it does not even create much heat.

 

[tpenfield]

I still wouldn't go cutting into an aluminum tank unless it had been purged and was full of CO2., but that's just me

 

[bennnyjw]

My next attempt is more to take a handsaw/hacksaw blade and try and run it down the side to loosen anything up. I had previously drained most of the tank. If it got so bad I had to cut the tank I would prob run a solution through it then put gas spill sand in to absord more. But thinking that won’t be needed.

thanks for all the responses. I will post more after I give it another shot.

And will most likely get another tank from rds for the exact fit.