How to repair a hole in a plastic outboard tank

[skipmac]

A $%@#$%!!! squirrel chewed a small hole in the bottom of my 6 gallon outboard tank. I really, really want to fix this so I don't have to deal with the new, sealed, CARB compliant, guaranteed to spew gas, non vented junk one has to buy in the US.

The tank is of course some kind of poly (PE or PP) and no conventional adhesives or caulks will stick. Previous research into working on PP and PE I learned that you can weld it like metal. So cut a strip from an another old, leaky jerry can and tried it. The gas tank acts like it is Teflon coated. I can melt the cut strip and heated the tank until it was ready to melt but the strip will not stick, even slightly. All I can guess is that over time the gas/oil (it's a 2 stroke engine) has permeated the plastic so nothing sticks. I even cleaned it with solvent, sanded the surface and tried again and zero luck.

So does anyone know of any kind of goop that will plug a very small hole in the bottom of my tank?

[deblen]

Originally Posted by skipmac

A $%@#$%!!! squirrel chewed a small hole in the bottom of my 6 gallon outboard tank. I really, really want to fix this so I don't have to deal with the new, sealed, CARB compliant, guaranteed to spew gas, non vented junk one has to buy in the US.

The tank is of course some kind of poly (PE or PP) and no conventional adhesives or caulks will stick. Previous research into working on PP and PE I learned that you can weld it like metal. So cut a strip from an another old, leaky jerry can and tried it. The gas tank acts like it is Teflon coated. I can melt the cut strip and heated the tank until it was ready to melt but the strip will not stick, even slightly. All I can guess is that over time the gas/oil (it's a 2 stroke engine) has permeated the plastic so nothing sticks. I even cleaned it with solvent, sanded the surface and tried again and zero luck.

So does anyone know of any kind of goop that will plug a very small hole in the bottom of my tank?

You cannot glue HDPE. It must be "welded" by melting a piece of HDPE into the base HDPE item-preferably using hot air as heat source.


Google or Youtube "welding HDPE"


Cheers/Len

https://www.youtube.com/watch?v=zavTvWQ-Xr4

[skipmac]

Originally Posted by deblen

You cannot glue HDPE. It must be "welded" by melting a piece of HDPE into the base HDPE item-preferably using hot air as heat source.


Google or Youtube "welding HDPE"


Cheers/Len

Hi Len,

Guess you missed the second paragraph where I addressed the failure in welding.

I had indeed watched the video you linked (and a couple of others) and tried welding but the melted poly would not stick to the tank. I speculated that over time gas/oil permeated the poly tank and prevents new poly from sticking when I tried to weld them together. And yes I did make sure both pieces were well heated and at melting temp. Put the two together, even worked them around with a metal tip, cleaned both with solvent, sanded. Nothing I tried would allow the melted plastics to stick to each other.

[thinwater]

Originally Posted by skipmac

A $%@#$%!!! squirrel chewed a small hole in the bottom of my 6 gallon outboard tank. I really, really want to fix this so I don't have to deal with the new, sealed, CARB compliant, guaranteed to spew gas, non vented junk one has to buy in the US.

The tank is of course some kind of poly (PE or PP) and no conventional adhesives or caulks will stick. Previous research into working on PP and PE I learned that you can weld it like metal. So cut a strip from an another old, leaky jerry can and tried it. The gas tank acts like it is Teflon coated. I can melt the cut strip and heated the tank until it was ready to melt but the strip will not stick, even slightly. All I can guess is that over time the gas/oil (it's a 2 stroke engine) has permeated the plastic so nothing sticks. I even cleaned it with solvent, sanded the surface and tried again and zero luck.

So does anyone know of any kind of goop that will plug a very small hole in the bottom of my tank?

No, there is no safe repair. The gas is in the plastic (old-school permiable, right?) and no repair will be safe. (many years in the refining business, including problems with FRP and PE tanks)

The new CARB stuf is not junk, you probably just need to learn to understand it.

A gas tanks should NOT be vented when not in active use, unless you want water in your e10 and carb problems. I keep my vent closed when not running the engine.

The tanks are intended to be fitted with an in-line demand valve. Attwood makes them -- Google. Alternatively, fit a shut-off valve between the motor and the tank. The tank should include a vacuum break.

Keep the tank out of the sun or cover it or paint it white. Overheating will cause serious pressure.

---

It's a compromise. On one hand, this preserves valuable volitiles that ease starting and help keep the carb clean. On the other hand, you do need to install them properly, which is common. I see them as an improvement in engine reliability.


---


And I suggest smearing something nasty tasting, like grease, on the bottom of the tank, for the squirrels.

[wingssail]

How about screwing a small plate over the hole using sealant or some oil based permatex as a gasket.

But for gasoline storage, probably need to buy a new tank.

Local people in many places in the world just use any old plastic jug with a hose stuck through a hole in the cap.

[rslifkin]

I'm with Thinwater on this one. Mind you, I don't regularly disconnect the fuel line for my dinghy outboard (as our dinghy gets hoisted with the outboard on). I've got one of the newer tanks and added a demand valve to the fuel line. In general, it just works. Open the vent, fire up the outboard, and go. Close the vent after shutdown. With the demand valve it's not an issue if the tank is pressurized (no need to release the pressure). And the vent will admit air as needed to avoid building a vacuum while running.

Better sealed tanks are always good for gas. The fuel lasts much longer and things don't gum up as easily. That's why modern cars with fuel injection and well sealed fuel systems rarely have fuel issues. The fuel sees very little air exposure.

[skipmac]

Originally Posted by thinwater

No, there is no safe repair. The gas is in the plastic (old-school permiable, right?) and no repair will be safe. (many years in the refining business, including problems with FRP and PE tanks)

The new CARB stuf is not junk, you probably just need to learn to understand it.

A gas tanks should NOT be vented when not in active use, unless you want water in your e10 and carb problems. I keep my vent closed when not running the engine.

The tanks are intended to be fitted with an in-line demand valve. Attwood makes them -- Google. Alternatively, fit a shut-off valve between the motor and the tank. The tank should include a vacuum break.

Keep the tank out of the sun or cover it or paint it white. Overheating will cause serious pressure.

---

It's a compromise. On one hand, this preserves valuable volitiles that ease starting and help keep the carb clean. On the other hand, you do need to install them properly, which is common. I see them as an improvement in engine reliability.


---


And I suggest smearing something nasty tasting, like grease, on the bottom of the tank, for the squirrels.

I take your point about proper care of the tanks but it's a bit of a pain. No place out of the sun in a small dinghy and it doesn't take long at all for the tank to overheat and swell if you leave it at a dock in the sun for just an hour or two. So then you have to remember to loosen the fill cap a little to prevent pressure build up, then remember to tighten again when you get back in the dinghy to keep from spilling gas. Then if it cools off a lot at night you end up pulling a vacuum in the tank.

Maybe I don't know the trick but this is all I know how to do.

If not using the motor for a while I will close the vents and additionally if not using it for a month or two, I try not to store the gas at all. Even with Stabil it doesn't seem to keep well.

[rslifkin]

Originally Posted by skipmac

I take your point about proper care of the tanks but it's a bit of a pain. No place out of the sun in a small dinghy and it doesn't take long at all for the tank to overheat and swell if you leave it at a dock in the sun for just an hour or two. So then you have to remember to loosen the fill cap a little to prevent pressure build up, then remember to tighten again when you get back in the dinghy to keep from spilling gas. Then if it cools off a lot at night you end up pulling a vacuum in the tank.

Maybe I don't know the trick but this is all I know how to do.

If not using the motor for a while I will close the vents and additionally if not using it for a month or two, I try not to store the gas at all. Even with Stabil it doesn't seem to keep well.

The newer tanks are meant to handle a decent amount of pressure without hurting the tank. They'll vent pressure if it reaches 5 psi IIRC to avoid the tank exploding. If you have a demand valve in the fuel line it won't feed that pressure to the outboard so there's no risk of forcing fuel past the carb needle and seat (or damaging the fuel pump) and therefore no need to vent off the pressure from the tank.

[skipmac]

Originally Posted by rslifkin

I'm with Thinwater on this one. Mind you, I don't regularly disconnect the fuel line for my dinghy outboard (as our dinghy gets hoisted with the outboard on). I've got one of the newer tanks and added a demand valve to the fuel line. In general, it just works. Open the vent, fire up the outboard, and go. Close the vent after shutdown. With the demand valve it's not an issue if the tank is pressurized (no need to release the pressure). And the vent will admit air as needed to avoid building a vacuum while running.

Better sealed tanks are always good for gas. The fuel lasts much longer and things don't gum up as easily. That's why modern cars with fuel injection and well sealed fuel systems rarely have fuel issues. The fuel sees very little air exposure.

My concern is in the hot Florida sun the tanks get extremely pressurized to the point of swelling up like a beach ball. That makes me a bit nervous and, while it hasn't happened to me, I have friends that had failures and catastrophic leaks from the high pressure.

[skipmac]

Originally Posted by rslifkin

The newer tanks are meant to handle a decent amount of pressure without hurting the tank. They'll vent pressure if it reaches 5 psi IIRC to avoid the tank exploding. If you have a demand valve in the fuel line it won't feed that pressure to the outboard so there's no risk of forcing fuel past the carb needle and seat (or damaging the fuel pump) and therefore no need to vent off the pressure from the tank.

I have read the bit about venting at 5 psi. Not sure if the vent failed or I had an old tank without the overpressure valve or if 5 psi is more than I realize but I've come back to the dink after a couple of hours at the beach to see the gas tank looking very round; as sides, top and bottom bulging out close to a couple of inches.

[rslifkin]

The tanks do bulge noticeably before they start releasing pressure. Keeping it somewhat shaded does help a lot, however. Mine is mostly under one of the dinghy seats and while I've seen it swell, I've never seen it swell far enough to concern me.

[JPA Cate]

Skipmac: Relative to covering the tank. Sunbrella tank covers are easy to make: a top piece, and one long one for the perimeter; then, mark for the opening for the fuel gauge and fuel attachment. You might want to use the icebox white, and make at least the top two layers. It won't look pretty when it gets fuel & oil on it, but don't worry, it should give a lot of relief from the heat for it. You can also try some heavy duty, BBQ weight, reynolds wrap between the layers, shiny side up.

New tank, maybe a trip out of country?

Ann

[skipmac]

Originally Posted by JPA Cate

Skipmac: Relative to covering the tank. Sunbrella tank covers are easy to make: a top piece, and one long one for the perimeter; then, mark for the opening for the fuel gauge and fuel attachment. You might want to use the icebox white, and make at least the top two layers. It won't look pretty when it gets fuel & oil on it, but don't worry, it should give a lot of relief from the heat for it. You can also try some heavy duty, BBQ weight, reynolds wrap between the layers, shiny side up.

New tank, maybe a trip out of country?

Ann

Thanks Ann. Does a cover make that much difference? Guess I'll give it a try.

[Jammer]

Skipmac,


Welding PE is hard. Both pieces have to have a layer of liquid on the surface when bonded, and you have to hold the patch firmly in place while it cools (gloves, natch). Preheating is important. It can be done but may take several tries.


You can glue PE if you flame treat it first and use G/Flex epoxy, and I have done this with good results.


For a while I was using metal gas tanks for my outboards. They are readily available used, at least here, and if cleaned up work well. I like to use the 60s/70s Johnson/Evinrude ones, which can work with any kind of motor, as long as you make up a hose with the correct ends. Parts are still available so you can fix the fuel gauge, valves, etc. I'm not sure it was worth it.


Last year I got a new 9.9 and it came with a (CARB-compliant) plastic tank. It works fine really and I haven't changed it out.

[Jammer]

Originally Posted by rslifkin

If you have a demand valve in the fuel line it won't feed that pressure to the outboard so there's no risk of forcing fuel past the carb needle and seat (or damaging the fuel pump) and therefore no need to vent off the pressure from the tank.

Some outboards manufactured before the CARB era have problems with flooding from this.


In southern states and tropical areas the gasoline you buy should have relatively low vapor pressure. The real basketball-shaped tanks come from running winter gas (which has butane in it) the following spring and summer. It happens to people who hunt ducks in the fall, or otherwise have an extended fall boating season.