Need advice on opening/closing aluminium fuel tank!

[ThePinkPanther]

I have a 260 litre tank in my Whittley that has a crack in the internal "spear pipe" and as the fuel tank cannot be removed without semi demolishing the boat, I have to cut into the top of the tank and either remove/repair the spear or fit a new one.

After draining the fuel tank, I figure on filling it with water right to the brim and then drilling a few holes to allow a hand hacksaw to take out a square panel about 200 x 200 mm.

That size will allow me to give the old tank a good clean out and then I will refit an oversized alu panel with a gasket and metal threads.

I want to avoid any welding due the obvious danger and the impossibility of removing the tank.

Anybody got any safety or clever ideas on removing/replacing the panel? This is an easily accessable part to work on.

Not as yet sure what fitting the (new) spear will have for attachment to the tank top but would imagine that a gasket and more metal threaders would do that job.

Andy advice on spear pipe internal diameters but I can copy the dead one once I can see what is going on.

The "crack" was finally located by topping up the tank until it stopped sucking air through the outlet pipe to the carby that was causing all sorts of engine problems.

[Chimo]

Where are you?

Chimo

[ThePinkPanther]

Raby Bay on the Bayside of Brissy!

[finga]

How big (dia) is the cracked pipe?
How much of it sticks up (or is it from the side) out of the tank before the flexible hose goes onto it?
You've got the Mercruiser haven't you matey?
What's her fuel economy per hour?

[pedrodepacus]

hey mate just a couple of things firstly do you have any idea how thick the material in the tank is as in 3mm or 4mm are you planning to put the threads directly into the tank material.
can you access the bottom or a low point of the tank from the outside to put a bsp elbow fitting in and connect the fuel line to that

[ThePinkPanther]

Thanks guys, I haven't as yet "made the cut" so speak so unsure of thickness of aluminiun etc. but what I plan on doing re the new (alu) spear is to have it welded to the rear of the new top plate and in that way I can ensure it is pretty well in the same place as the old one and solidly attached, right ID etc.

Also a lot easier to work on "ex the boat" rather than muck about once the new plate is fitted. In this latter issue, leaning towards the new fuel resistant silicons and a few metal threaders...................

I suspect the tank is about 3 mm but will have a better idea tomorrow when I slice it's lid off!

Thanks again!

[Chimo]

PinkPanther

Listen to Pedrodepacus, better still, get him to fix it for you: he bulds al and ss tanks and repairs the buggers too.

Shame I didn't know of him before I replaced my leaking SS 250 lt job that people told me couldn't be fixed!

Cheers
Chimo

[sharkcat one]

Hi guys,

Alloy fuel tanks are the worst things ever invented, their only in boats because they are cheep to build.
My advise would be to cut off the lid , cut the baffels out , get someone to build you either a s/s or fibreglass tank which will fit inside your alloy tank ( only if it is to hard to remove ).
This time it may be the pick up pipe, in 6mths it maybe a weld that cracks or corrosion or pitting or sludge build up . These tanks can corrode from the inside out. Talk to a boatbuilder , shipwright or engineer who has had to replace a alloy tank in a 15 to 20 year old boat , you will find by this time these tanks are no good. Don't talk to a alloy welder as they only see the tank when they build them ,not in 15 to 20 years. S/S tanks can crack on welds ( not very common but can happen ) the best tanks to have are fibreglass either for diesel or unleaded ( do not put blended fuels into a fibreglass tank ) . About 70% of fuel tanks in a servo are made from fibreglass . Fibreglass tanks will move with the boat without cracking and have a much higher life span . Draw backs are slightly heavier and cost more.

Cheers

[Owen]

You have several options.

1: Do as you have planned, but success will depend on material thickness.

2: You could create a sandwich affair with a gasket.
e.g.
Drill a 50mm hole in the tank.
Make your top plate with tube say 75mm dia.
Make a bottom plate out of thick material say 60 mm with a hole in the middle for the tube to pass through.
Drill and tap screw holes in the bottom plate such that the hole patern is less than 50mm to the outside of the holes. Put a flat on two sides so that you can slide the bottom plate through the hole. Make a gasket to fit and assemble the hole shebang. You can then tighten it to clamp up and seal it.
This way it doesn't matter what thickness it is, but it's tricky and of course any gasket can eventually leak. No more likely than a fuel sender though.
I'd use some "stag" sealer on the sucker for added insurance.


3: Make your top plate and tube. Drill a hole big enough for the tube and drop in. Drill holes for pop rivets all around the edges (every 15-20m).
Now you have to get ALL the filings out of the tank!!
Put a generous amount of 24hr araldite on and pop it all up. Cover all the rivets with araldite to seal them completely.
This is how many race car tanks are sealed when foam filling them.
Be sure to use stainless rivets.

[bobbyb]

hi pinky.
if it was me I'd take steps now to make the fuel tank removable for future dramas.

[ThePinkPanther]

Thanks again guys!

Geez, this is turning into a nightmare!

Short of cutting up the whole floor and ripping out the drivers cabinet seats, there is no way to to get the tank out in one piece. Easier to buy a new boat!

I am hoping that when I cut out the top piece, I will be able to find just where the crack/leak is on the spear or it's attachment to the outflow pipe.

If that is possible then I can either have it welded or maybe try some of the fancy epoxy stuff around to plug the hole or whatever.......................

To reseal the cutout, I would be content with getting an oversize piece of 3 mm aluminium and with a gasket and/or some fuel resistant silicone or better yet STAG, simply refit the new section and a few metal threaders for good measure.

The air leak ceased the instant I filled the tank slightly above half so I am guessing the problem lies somewhere in the piping at that level. The tank itself is definitely not cracked.

If the old spear is unfixable, I would like to play tricky and attach the new spear pipe to the piece of aluminium plate used to recover the hole. That could be easily welded in place and thereby have an all-in-one cover to install.

I have to pick up a manual petrol getter-outter pump tomorrow morhing so all will be known when I empty the tank and cut out the section to see what is going on.

Again, many thanks for all the advices!!

[Spaniard_King]

Fuel tank issues need to be fixed properly and adding another possible leak point is not the best option IMO

Yes it sounds a big job to cut it out and repair/replace but may be cost effective in the long run. Any good fiberglasser should be able to cut thew tank out and glass it back in without too much dramma.

Leaking fuel into the hull is not a good situation.. try to avoid it at any cost IMO

[sharkcat one]

Just one thing Pink Panther don't use epoxy near fuel , what is better than stag is SIKA ( not silcon ) as silcon is no good with fuel either but sika is excellent.
Fuel will eat away epoxy and silcon over time.

Cheers.

[Mr__Bean]

Before you hack into the tank are you 100% the problem is within the tank?

Fuel line air leaks and fuel pump issues can also occur as the fuel level goes down and the has to suck harder to lift the fuel higher.

Have you triple checked all of the fuel lines?

The bottom half of the dip tube failing just doesn't sound right to me.

- Darren

[trueblue]

new fuel tank time...

[cormorant]

What ID is the current spear and what ID does your motor require?

If the spear is the issue (and I haven't seen one corrode half way up - seen en bent and snapped at welds etc where they are manufactured and not supported next to a a baffel or not strong enough pipe ) it would be very easy just to sleeve the old spear internally with some new pipe. and use a second pipe clamp at the top to seal both off and it would also prove that it was the pickup that was stuffed.


If you have tp go ibto teh tank a smaller 100mm hole is always better and a oval or rectangular shape as it allows you to insert and fix a backing plate. A square or circle don't allow this . If you keep it a standard size there would be spare parts of nitrile fuel sender gaskets avaliable.

As always be aware of danger of fuel fumes , it's not the fuel but the fumes taht start the explosion.