How to repair a hole in a plastic outboard tank

[s/v Jedi]

Originally Posted by 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.

Indeed, I did the flame treatment on schedule 40 PVC and suddenly it was okay being fiberglassed and it’s strong as can be still after many, many years.

I never did PE welding though. I think I would try hot-gluing a patch over the hole, then use a “stick” of PE and hot air or even a small torch to melt patch, stick and also a tiny bit of the tank and solder/braze it on like that. I tried this with some plastics and it worked.

[rslifkin]

Originally Posted by Jammer

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

That's what the demand valve is for. It prevents the tank pressure from pressurizing the outboard. The demand valve has an outside air pressure reference and only allows flow when the engine starts to pull a vacuum on the line, so the line after the demand valve doesn't get above atmospheric pressure even if there's 5 psi in the tank.

[Jammer]

Originally Posted by s/v Jedi

I never did PE welding though. I think I would try hot-gluing a patch over the hole, then use a “stick” of PE and hot air or even a small torch to melt patch, stick and also a tiny bit of the tank and solder/braze it on like that. I tried this with some plastics and it worked.

Some years ago I dabbled in hydroponic vegetables, mainly lettuce. I grew lettuce on a flood table that was made out of a cheap plastic underbed tub. You know, the kind of plastic tray that you can buy at Target/Walmart/etc that has little rollers and that you can slide under a bed in your apartment for more storage. They're cheap, they're made of PE, and in order to get the flood table to work I had to have a leakproof hose barb at the low point in the thing.


I bought a PE hose barb and while it took several tries, once I got it, it was leakproof and very solid. I hooked up an aquarium powerhead and a timer in a 5 gallon bucket below and flooded the table once every 15 minutes, and grew all kinds of lettuce in February in Minnesota. I spent a lot of money on electricity that year and decided for a variety of reasons not to repeat the experiment.

[Chotu]

I have gone through a lot of tanks in Florida. Jerry cans, outboard tanks.

The constant Beachball to shriveled in box process on a daily basis kills them.

They sort of de laminate, and then they just break apart.

[wsmurdoch]

Take your old tank's cap and go shopping for your new tank. Pick one that your old cap with the vent screw fits. Presto, you have a vented new tank, and you have a spare cap to boot. My old vented Scepter gas tank cap fitted my new Scepter gas tank.

Or, buy a Scepter fuel tank https://www.basspro.com/shop/en/scep...able-fuel-tank and a vented cap to go with it https://www.basspro.com/shop/en/scep...ented-fuel-cap .

[skipmac]

Originally Posted by wsmurdoch

Take your old tank's cap and go shopping for your new tank. Pick one that your old cap with the vent screw fits. Presto, you have a vented new tank, and you have a spare cap to boot. My old vented Scepter gas tank cap fitted my new Scepter gas tank.

Or, buy a Scepter fuel tank https://www.basspro.com/shop/en/scep...able-fuel-tank and a vented cap to go with it https://www.basspro.com/shop/en/scep...ented-fuel-cap .

Thanks. Had tried the cap from one old tank on a new one and the threads did not match so had assumed the new tanks had intentionally used some odd ball thread to prevent just this. But have another cap and will try that one on a couple of new style tanks as well.

But will also check out the Scepter tanks. You aren't the first to mention them.

[skipmac]

Originally Posted by 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.

I do have an old, metal tank I inherited from my father that's in good condition. But as mentioned, they do tend to leave rust rings but read about a sure cure. You can get split plastic tubing that is used for various applications and run that around the bottom of the tank. Now just have to see if I could either change the fittings on the tank or hose so it will connect to my Yamaha.

[GreenWave]

Amazon still selling this tank which looks to have the fuel cap vent


https://www.amazon.com/dp/B01BNBCS5Y...v_ov_lig_dp_it

[ItDepends]

I am confused...why are the new tanks giving people trouble?

We have one. CARB standard, about 3 years old. It is tied to the rail, like our two jerry jugs. In the full sun, in the tropics. We spent this summer at 10N, so I think that trumps even Florida sun.

Yes, in the full sun it swells, and then shrinks in the cold. Guess what? It is MADE TO DO THAT! Never leaks a drop. Looks like new. The jerry jugs are made of cheaper plastic, they do the same, and they last about 3 or 4 years before the UV kills them. Someday when I have a sewing session on the task list I might make covers, but it hasn't been a priority.

The fuel tank is pretty trivial to use: Put in dinghy; Crack open cap to even out pressure; Connect hose; Close cap; Open vent; Start engine.

Done with engine? Close vent; Disconnect hose.

What is so hard?

Our engine is a 2-stroke Yamaha with a fuel pump and carburetor that was designed decades ago. There isn't anything "special" about them to deal with the pressure behavior of modern fuel tanks.

I do have issues with crappy design of many of the CARB jerry jug nozzles, but that's a whole other thread (you can look it up...)

[ItDepends]

Originally Posted by GreenWave

Amazon still selling this tank which looks to have the fuel cap vent


https://www.amazon.com/dp/B01BNBCS5Y...v_ov_lig_dp_it

They ALL have a vent somewhere.

Air has to get in while you are sucking fuel out. The difference between the "new" tanks and the "old" ones is the new tanks have a one-way vent that only allows air to flow into the tank, and keeps gasoline vapors from getting out. In theory, at least.

[tamicatana]

G/Flex. Follow directions, including flame treating

Squirrel Fricassee:
Shoot squirrel. Gut and skin. Wash the carcass. In a skillet, add butter, onions ("trinity") and garlic. Brown the seasoning. Add the squirrel carcass, browning the meat. Add some flour and make a roux. Add a little water to make a gravy. Simmer until the squirrel is done, probably about 20-30 mins

[Rumrace]

PETG it’s awesome plastic one time use. Your tank is a total loss. Super glue, dura tape, tree sap, laser, small torch, glue gun nothing will stick to the stuff. Which is kinda great.
Sorry
Heat to fuse it was only 225c but now would take 400c where it’s structure fails. 50 other plastics you can glue anything to.

[wsmurdoch]

Gasoline outboard motor fuel tanks are commonly made of polyethylene either high density polyethylene (HDPE) or crosslinked polyethylene (XLPE) now usually with an inner liner material to provide a barrier to vapor transmission.

PETG is glycol modified polyethylene terephthalate. Most commonly the term is associated with Eastman Chemical company's ESTAR 6763 (PETG 6763) which is a polymer of terephthalic acid, ethylene glycol, and cyclohexane dimethanol (the modifying glycol). It is a polyester.

[JBsurfin]

Originally Posted by skipmac

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.

Its worth the danger of a bad wield? Time to bite(no pun intended) the bullet and purchase new or used if located.

[Seabeau]

An easy solution to the tank degradation by UV and over pressurization is to cover a new plastic tank with white latex paint. First wash the tank with soap and water, then wipe down with acetone or alcohol. Let the acetone/alcohol dry, then use several light coats of exterior grade latex paint. Touch up as needed.